Brominated Anionic Styrenic Polymers and Their Preparation

ABSTRACT

Concurrently fed into a reaction zone held at about 10° C. or less are brominating agent, aluminum halide catalyst, and a solution of anionic styrenic polymer having a GPC Mn about 2000-30,000. The components are in at least two separate feed streams. The feeds are proportioned to maintain (a) the amount of aluminum halide being fed at about 0.8 mole percent or less based on the amount of aromatic monomeric units in the polymer being fed, and (b) amounts of brominating agent and unbrominated polymer in the reaction zone that produce a final washed and dried polymer product containing about 60-71 wt % bromine. The catalyst is deactivated, bromide ions and catalyst residues are washed away from the reaction mixture, and the brominated anionic styrenic polymer is recovered and dried. The dried polymer has a volatile bromobenzene content of about 600 ppm (wt/wt) or less as well as other beneficial properties.

REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 11/612,991,filed Dec. 19, 2006, now allowed, which in turn claims the benefit andpriority of U.S. Provisional Application No. 60/753,285, filed Dec. 21,2005, the disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

This invention relates to processes for the preparation of brominatedanionic styrenic polymers having reduced contents of bromobenzenes, andto the novel brominated anionic styrenic polymers that can be producedby such processes.

BACKGROUND

Commonly-owned U.S. Pat. Nos. 5,677,390, 5,686,538, 5,767,203,5,852,131, 5,852,132, 5,916,978, 6,133,381, 6,207,765, 6,232,393,6,232,408, 6,235,831, 6,235,844, 6,326,439, and 6,521,714 describe whatis believed to be the best known prior process technology for producingbrominated styrenic polymers such as brominated polystyrene having thebest known properties of any previously-known brominated styrenicpolymer. In this connection, the terms “brominated styrenic polymer” and“brominated polystyrene” as used anywhere herein including the claimsrefer to a brominated polymer produced by bromination of a pre-existingstyrenic polymer such as polystyrene or a copolymer of styrene and atleast one other vinyl aromatic monomer, as distinguished from anoligomer or polymer produced by oligomerization or polymerization of oneor more brominated styrenic monomers, the properties of the latteroligomers or polymers typically being considerably different frombrominated polystyrene in a number of respects.

In producing brominated anionic styrenic polymers by bromination ofanionic styrenic polymers, bromobenzene impurities tend to be formed ingreater than desired quantities. Among these impurities are species inwhich benzene rings can be substituted by 2 to 6 bromine atoms. Becauseof their greater volatility at elevated temperatures encountered inmolding, the species containing 2, 3, or 4 bromine atoms as ringsubstituents are more undesirable than those containing 5 or 6 bromineatoms on the ring. In the case of bromination of anionic polystyreneusing aluminum halide catalysts in which the halide atoms are bromine orchlorine or both, the species containing 2, 3, or 4 bromine atoms asring substituents as determined by NMR are, respectively,1,4-dibromobenzene, 1,2,4-tribromobenzene, and1,2,4,5-tetrabromobenzene. These volatile species have a strong odor andare considered to be skin and lung irritants. Also, the formation ofthese species in the process results from cleavage of aromatic ringsfrom the polymer chain. This in turn introduces irregularities in thepolymer chain and/or addition of bromine atoms to the polymer chain.Such addition results in reducing the thermal stability of thebrominated styrenic polymer. Thus, it would be highly advantageous if away could be found for reducing the formation of bromobenzeneimpurities, especially the more volatile dibromo, tribromo and/ortetrabromo species, during the actual preparation of brominated anionicstyrenic polymers rather than relying upon purification steps duringproduct workup or purification.

BRIEF SUMMARY OF THE INVENTION

This invention provides process technology which can significantlyreduce the amounts of more volatile bromobenzenes present in finishedbrominated anionic styrenic polymer products without need for specialproduct workup or special purification procedures. The reduction in theamounts of such bromobenzenes in the finished products does not relyupon use of special workup or special purification procedures to achievesuch reductions. Instead, conventional workup and drying procedures canbe used and yet the product will contain low amounts of volatileundesirable bromobenzenes, i.e., no more than 600 ppm (wt/wt) and inpreferred cases, 300 ppm (wt/wt) or less.

More particularly, in accordance with this invention there is provided aprocess of preparing brominated anionic styrenic polymer having areduced volatile bromobenzene content, which process comprises:

-   A) concurrently feeding into a reaction zone components comprised    of (i) a brominating agent (preferably bromine), (ii) aluminum    halide catalyst in which the halide atoms are bromine or chlorine or    both, and (iii) anionic styrenic polymer (preferably anionic    polystyrene) having a GPC number average molecular weight in the    range of about 2000 to about 30,000 (preferably in the range of    about 2000 to about 10,000 and more preferably in the range of about    3000 to about 7000) in the form of a solution or slurry in a solvent    to form a reaction mixture, wherein said components are fed (1)    individually as at least three separate feeds or (2) as at least two    separate feeds, one feed of which contains no more than two of (i),    (ii), and (iii), and another feed of which contains the third of    (i), (ii), (iii) either individually or in combination with no more    than one other of (i), (ii), and (iii), to thereby form a reaction    mixture containing a liquid phase, and maintaining said reaction    mixture at about 10° C. or less whereby bromination of anionic    styrenic polymer occurs, the components being proportioned such that    the amount of aluminum halide being fed is at about 0.8 mole percent    or less in relation to the molar amount of aromatic monomer units in    the anionic styrenic polymer being fed, and such that the dried    brominated anionic styrenic polymer referred to in C) hereinafter    will have a bromine content in the range of about 60 to about 71 wt    % (and preferably in the range of about 67 to about 69 wt %);-   B) deactivating the catalyst in, and washing away bromide ions and    catalyst residues from    -   1) substantially the entire reaction mixture or    -   2) portions of the reaction mixture that have exited from the        reaction zone; and-   C) recovering brominated anionic styrenic polymer product from the    reaction mixture and drying such product whereby the dried    brominated anionic styrenic polymer has a bromine content in the    range of about 60 to about 71 wt % (preferably in the range of about    67 to about 69 wt %) and a volatile bromobenzene content which is no    more than about 600 ppm (wt/wt), and preferably is about 300 ppm    (wt/wt) or less.    Preferably in B), the catalyst is deactivated by quenching the    reaction mixture in an aqueous quenching medium.

If the concurrent feeds of A) above unify (i), (ii) and (iii), forexample in a feeding device such as an injector, probe, or nozzlefeeding to or into a reaction mixture in a reactor, such unifiedcontents within such feeding device constitute a portion of the reactionzone. When, in a case of this type, such concurrent feeds are continuousconcurrent feeds, better temperature control is achieved by ensuringthat the unified contents are caused to exit from such feeding deviceand enter the main body of the reaction mixture in the reactor within nomore than about 5 seconds and preferably no more than about 2 secondsafter unification in the device. And when, in a case of this type, atleast one of such concurrent feeds is a rapidly pulsed concurrent feed,better temperature control and greater reaction mixture uniformity areachieved by ensuring that the unified contents are caused to exit fromsuch feeding device and enter the main body of the reaction mixture inthe reactor within no more than about 5 seconds and preferably no morethan about 2 seconds after unification in the device.

It can be seen therefore that in conducting A) above components (i),(ii), and (iii) are in at least two separate feed streams and one ofthem, preferably (iii), is kept separate from at least one of (i) and(ii), preferably from both of (i) and (ii), until the at least twoseparate feeds of (i), (ii) and (iii):

-   1) directly enter the main body of the reaction mixture in the    reactor such as a stirred tank reactor or a tubular or loop-type    reactor, and/or-   2) are unified no more than 5 seconds (and preferably no more than 2    seconds) before directly entering the reaction mixture in the main    body of the reaction mixture in such a reactor.

In a preferred mode of operation, the above process is carried out in aclosed reaction system whereby the hydrogen bromide coproduct is kept inthe reaction mixture until the catalyst is deactivated, preferably in anaqueous quenching system. Because HBr coproduct is soluble in thehalogenated solvent used, the HBr coproduct is thus carried through theclosed reaction zone while in solution, and in fact serves as anadditional diluent thereby reducing the viscosity of the polymericsolution. During bromination, the closed bromination system remainsunder autogenous pressure which is typically up to about 60 psig. Thispreferred mode of operation provides several tangible advantages. In thefirst place, the typical need for a scrubbing system for recovery of HBrcoproduct from the exit gas stream from the bromination reactor iseliminated. Instead of providing and using such a scrubbing system, thebromine values of the HBr coproduct can all be recovered in a singleoperation from the contents of an aqueous quenching system used fordeactivating the catalyst. Moreover, the capital cost for a scrubbingsystem and the costs involved in the maintenance of a scrubbing systemare eliminated. In addition, the viscosity of the reaction mixture inwhich the HBr is retained is reduced as compared to a similar reactionsystem in which HBr has been removed. Such a reduction in viscosityoffers the opportunity of operating with less solvent or enable use of amoderately higher molecular weight of an anionic styrenic polymer withthe same level of solvent.

Pursuant to the practice of this invention there are also provided newbrominated anionic styrenic polymer compositions having bromine contentsin the range of about 60 to about 71 wt % (preferably in the range ofabout 67 to about 69 wt %), bromobenzene contents which are no more thanabout 600 ppm (wt/wt) and preferably 300 ppm or less, and additionaldesirable properties or characteristics, especially a thermal ΔE colorvalue of about 15 or less and/or a thermal stability in the 320° C.Thermal Stability Test of about 125 ppm or less of HBr.

The above and other features and embodiments of this invention will bestill further apparent from the ensuing description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevational depiction of an injection system forfeeding reactants, solvent, and catalyst into a reaction zone in thepractice of this invention.

FIG. 2 is a schematic flow diagram of a system for conducting acontinuous process in accordance with this invention.

FIG. 3 is a schematic flow diagram for conducting a continuous processin accordance with a preferred embodiment of this invention.

FURTHER DETAILED DESCRIPTION OF THE INVENTION

As used anywhere herein including the claims, the term “bromobenzene”,whether in the singular or plural, refers to one or more brominatedaromatic hydrocarbons formed as one or more coproducts or impurities inthe bromination reaction itself. The benzene ring may contain one ormore substituents other than one or more bromine atoms. For example itis likely that if an anionic styrenic polymer formed in whole or in partfrom a methylstyrene is subjected to bromination in the process, atleast some of the “bromobenzene” coproduct formed will be bromobenzeneshaving methyl and/or bromomethyl substituents on the ring. Thus“bromobenzene” or “bromobenzenes” as used anywhere herein including theclaims in connection with impurity formation or impurity content is notto be taken literally—instead these terms are used to represent thebrominated aromatic impurities that form during the bromination of theanionic styrenic polymer selected for use in the process. The term“volatile bromobenzene”, whether in the singular or plural, denotesbromobenzene species having in the range of 1 to 4 bromine atomsdirectly attached to the benzene ring of the bromobenzene, which, in thecase of bromobenzenes formed when producing brominated anionicpolystyrene, are comprised of one or more of dibromo, tribromo, and/ortetrabromo species, typically 1,4-dibromobenzene, 1,2,4-tribromobenzene,and/or 1,2,4,5-tetrabromobenzene.

Similarly as used anywhere herein including the claims, the terms“anionic styrenic polymer” and “anionic polystyrene” are terms commonlyused by those of ordinary skill in the art to denote, respectively, astyrenic polymer or polystyrene made by use of an anionic polymerizationinitiator, such as, for example, a lithium alkyl. Thus, as is well knownto those of ordinary skill in the art, these terms do not mean that thepolymer itself is anionic.

In the embodiments of this invention wherein a closed reaction system isused, the term “closed reaction system” denotes a reaction system which,except for piping or conduits carrying the necessary components(including purging carrier gases, etc.) into and out of the brominationreaction zone and into and out of the catalyst deactivation zone, isclosed from its surroundings. In short, the system is designed such thatgaseous HBr coproduct does not escape from the system, but rather iscaused to travel from the bromination reaction zone into the catalystdeactivation zone for recovery in a suitable form.

Bromination Process Technology

The processes of this invention can be conducted as a batch orsemi-batch process, or as a continuous process. Among the features ofthe process are:

-   1) concurrently feeding into a reaction zone, (i) a brominating    agent (preferably bromine), (ii) aluminum halide catalyst in which    the halide atoms are bromine or chlorine or both, and (iii) anionic    styrenic polymer (preferably anionic polystyrene) having a GPC M_(n)    in the range of about 2000 to about 30,000 (preferably in the range    of about 2000 to about 10,000, and more preferably in the range of    about 3000 to about 7000) in the form of a solution or slurry    (preferably as a solution) in a solvent;-   2) conducting the feeding of (i), (ii), and (iii) in at least two    separate feed streams and wherein no such feed stream is formed from    all three of (i), (ii), and (iii) except where the feeds are    unified, e.g., within a feeding probe, injector or nozzle no more    than 5 seconds and preferably no more than 2 seconds before leaving    the feeding probe, injector or nozzle and entering (preferably    directly entering) the main body of the reaction mixture in a larger    reactor, and preferably feeding (i), (ii), and (iii) as separate    feeds or combining (i) and (ii) as a single feed which is fed    separately from (iii);-   3) maintaining the reaction zone at about 10° C. or less, preferably    about 5° C. or less, more preferably in the range of about −2° C. to    about 3° C., to provide a reaction mixture containing a liquid    phase;-   4) proportioning the feed components to maintain the amount of    aluminum halide as it is being fed into the reaction mixture at    about 0.8 mole percent or less based on the molar amount of monomer    units in the anionic styrenic polymer as it is being fed into the    reaction mixture;-   5) proportioning the feed components to maintain amounts of    brominating agent and anionic styrenic polymer fed in the reaction    zone so that the final washed and dried brominated anionic styrenic    polymer product formed contains in the range of about 60 to about 71    wt % of bromine, and preferably in the range of about 67 to about 69    wt % of bromine;-   6) deactivating the catalyst, typically by quenching (a) the entire    reaction mixture in a batch process operation or (b) portions of the    reaction mixture after removal from the reaction zone in a    continuous process operation, with an aqueous quenching solution    soon enough that the bromobenzene content of the washed and dried    brominated anionic styrenic polymer is no more than about 600 ppm    (wt/wt), and preferably is about 300 ppm (wt/wt) or less;-   7) preferably conducting the bromination in a closed reaction system    so that the coproduct HBr remains in the reaction mixture until the    catalyst is deactivated, preferably by quenching the reaction    mixture with and recovering the HBr coproduct in an aqueous    quenching medium.

Feed (iii), i.e., the solution or slurry of the anionic styrenicpolymer, should contain enough solvent to form a solution or slurry thatis flowable or pumpable.

Another feature of this invention is that although it might be expectedthat the bromination reaction rate would be reduced by operating in aclosed bromination reaction system so that the HBr coproduct remainswith the reaction mixture throughout the bromination, it has been foundthat for all practical purposes the bromination reaction rate appears tobe as fast as if the bromination was conducted at atmospheric pressure.

The molar amount of aluminum halide catalyst being fed to the reactionmixture and the molar amount of aromatic monomer units in the anionicstyrenic polymer concurrently being fed to the reaction mixture can bemaintained at or below the specified molar ratio limit, by use ofappropriate amounts of (ii) and (iii) in the feeds and by setting and/orcontrolling the respective feeds rates at which (ii) and (iii) aredelivered or charged into the reaction mixture in the reaction zone. Inthis connection, the ratio of the molar amount of aluminum halidecatalyst being fed and the molar amount of aromatic monomer units in theanionic styrenic polymer concurrently being fed is determined by use ofthe following expression:

${{Mole}\mspace{14mu} \% \mspace{14mu} {AIX}_{3}} = {\frac{\begin{matrix}{{Weight}\mspace{14mu} {of}\mspace{14mu} {{AIX}_{3}/}} \\{{Formula}\mspace{14mu} {Weight}\mspace{14mu} {of}\mspace{14mu} {AIX}_{3}}\end{matrix}}{\begin{matrix}{{Weight}\mspace{14mu} {of}\mspace{14mu} {{Polymer}/}} \\{{Formula}\mspace{14mu} {Weight}\mspace{14mu} {of}\mspace{14mu} {Monomeric}\mspace{14mu} {Unit}}\end{matrix}} \times 100}$

where the weights of aluminum halide catalyst (represented as AlX₃ inthe expression) and of the polymer are in the same mass units such asgrams or pounds.

Preferably the concurrent feeds in A) comprise one or more separateindividual feeds of (i), (ii), and (iii) or one or more separate feedsof (1) a combination or mixture formed from (i) and (ii) and (2) one ormore separate feeds of (iii). Desirably, the probes, injectors ornozzles for these streams are disposed such that the respective feedstreams therefrom exit directly into the body of the liquid phase of thereaction mixture in the reaction zone. It is also preferred that thesites where each of the separate feed streams for a feed of (i), (ii),and (iii) in which one of them (with or without another one of them) isseparate from the other two of them or a feed of all three of them fedseparately and individually emerges from the probes, injectors ornozzles directly into the liquid phase of the reaction mixture areproximate to the emergent site or emergent sites of the other feedstream or streams. In more preferred embodiments, at least one of theseparate feed streams is a combination of (i) and (ii) and at leastanother of such separate feed streams is (iii), and such feed streamsare fed subsurface into the reaction mixture or within the body of theliquid phase of the reaction mixture by means of concentric orcoaxially-aligned injection probes or nozzles, or by means of injectionprobes, injectors or nozzles in substantial face-to-face opposedalignment so that the feeds are directed towards each other fromproximate orifices. By “substantial face-to-face opposed alignment” ismeant that the respective axes of the streams emanating from the probes,injectors or nozzles confront each other in the same plane at a 180°displacement (i.e., they are directly opposed to each other on a commonaxis) or the axes of the streams confront each other in a common planeat an obtuse angular displacement (i.e., they are opposed to each otherby more than 90° in a common plane).

As noted above, in preferred embodiments the sites in the liquidreaction mixture where the respective feed streams enter or are injecteddirectly into the reaction mixture are proximate to each other. As usedherein, including the claims, the term “proximate to” denotes that thesites where the feed streams directly enter the reaction mixture areclose enough to each other that formation of unacceptable amounts ofinsoluble polymer due to cross-linking of the unbrominated or partiallybrominated anionic styrenic polymer does not occur. Such cross-linkingcan occur if the feed streams enter a reaction mixture at too great adistance from each other unless there is sufficient rapid agitation ofthe reaction mixture at very low temperatures (e.g., 0° C. or below) toprevent excessive cross-linked polymer formation from occurring.

Without being bound by theory, it does not appear unreasonable tosuggest that in the reaction mixture into which the concurrent feedstake place, three competing reactions can occur, viz., (a) the desiredbromination of the anionic styrenic polymer and (b) undesired alkylationof the anionic styrenic polymer by the chloro- and/or bromohydrocarbonsolvent being used (which can also lead to crosslinking of unbrominatedor partially brominated anionic styrenic polymer), and (c) theundesirable dealkylation of the polymers aromatic rings producingbromobenzene impurities and creating sites of thermal instability on thepolymer chain, all such reactions being catalyzed by the aluminum halidecatalyst being used. By cofeeding the reactants and catalyst inproportions and at the low reaction temperatures as described herein,and preferably so that the feeds rapidly come into intimate contact witheach other because of the proximate injector or probe feeding sitesemployed, the bromination reaction occurs much more rapidly than anycompeting alkylation or dealkylation reaction and once the desired highlevel of bromination has occurred the resultant brominated anionicstyrenic polymer product is more resistant to alkylation or dealkylationthan unbrominated or partially brominated anionic styrenic polymers.

When utilizing a preferred proximate feeding system, the maximumdistance between or among the entry sites of feed streams will depend onvarious factors such as the rate of agitation of the reaction mixture,the temperature of the reaction mixture, the velocities of therespective feed streams, the concentrations of the respective feedstreams, and the extent of solubility of the catalyst in the reactionmixture and/or the solubility, if any, of the catalyst in the feedstream. As a rule of thumb, in designing a feed system for acommercial-sized installation, it is desirable to keep the distancebetween or among the emergent sites of the feed streams from theirrespective injectors or probes in a commercial installation at no morethan about 4 inches unless exceptionally high rates of agitation andvery low reaction temperatures are used. The smaller the distance belowabout 4 inches, the better. Preferably, coaxial feeding or substantialface-to-face opposed alignment feeding of the feed streams is employed.Coaxial feeding results, for example, from use of concentric injectorsor probes extending subsurface into the liquid phase of the reactionmixture.

In continuous operation of the process, average reaction time or averageresidence time (i.e., the average time the reactants and catalysts arein contact with each other or, in other words, the time from initialcontact of the reactants and catalyst until deactivation of catalyst)will typically be up to about 30 minutes and preferably about 20 minutesor less. More preferred continuous processes of this invention involveaverage reaction times or average residence times in the range of about2 to about 10 minutes, more preferably in the range of about 2 to about5 minutes, and still more preferably in the range of up to about 2 or 3minutes. Such short residence times are made possible by the use of thealuminum halide catalyst and the unique feeding methods employed used inthe processes of this invention. In the case of batch type operations,quantification of reaction time is more difficult as reaction times canbe greatly affected by such factors as the scale of operation, theextent of agitation provided within the reactor, and the rate of heattransfer in the reaction system. Thus in keeping the reaction time shortenough to prevent formation of brominated anionic styrenic polymercontaining more than about 600 ppm (wt/wt) of bromobenzene impurities,recourse may be had to use of trial experiments. As rules of thumb,which should be of assistance in this regard, when operating at a 2000gallon scale, a period of up to 3 hours may be permissible whereas at a4000 gallon scale of operation, a period of up to 6 hours may bepermissible. While there is some scale-up effect in continuousoperation, the effect in such operation tends to be of lesser magnitudethan in the case of batch operation.

As noted above, the concurrent feeding of (i) a brominating agent,preferably bromine, (ii) aluminum halide catalyst in which the halideatoms are bromine or chlorine or both, and (iii) the anionic styrenicpolymer solution in a solvent is conducted such that (i), (ii), and(iii) are in at least two separate feed streams and wherein no such feedstream is formed from all three of (i), (ii), and (iii). Thus, there arefour basic ways of carrying out such feeding. These are:

-   1) feed (i), (ii), and (iii) as three separate feeds;-   2) feed a combination of (i) and (ii) as a single feed which is fed    separately from (iii);-   3) feed a combination of (ii) and (iii) as a single feed which is    fed separately from (i); and-   4) feed a combination of (i) and (iii) as a single feed which is fed    separately from (ii).    Combinations of two or more feeds of 1), 2), 3), and 4) are    possible. Also, any or all of the foregoing feeds can be introduced    at more than one location in the reaction zone. As non-limiting    examples, in the case of 1) there can be multiple separate feeds of    any of (i), (ii), and/or (iii). Similarly, in 2) there can be    multiple separate feeds of the combination of (i) and (ii) and/or    multiple separate feeds of (iii), and so on. Where two or more feeds    of (i), (ii), and (iii) are employed, it is desirable to have the    respective sets of feeds disposed such that their own feeds enter    the reaction mixture proximate to each other, even though the    respective sets of feeds are spaced-apart from each other. For    example, where at a first locus of a continuous stirred tank reactor    a feed of a mixture of (i) and (ii) and a separate feed of (iii)    exist, and at a second spaced apart locus of the same continuous    stirred tank reactor, a feed of a mixture of (i) and (ii) and a    separate feed of (iii) exist, the two feeds at the first locus    preferably are proximate to each other, and the two feeds at the    second locus preferably are proximate to each other. However, there    is no need to have all four of such feeds proximate to each other.

Feeding as in 1) or 2) above is preferred, and feeding as in 2) above ismore preferred.

In the case of feeding as in 3) above, it is desirable to use achlorine-free organic solvent such as dibromomethane or1,2-dibromoethane to avoid degradation of the catalyst. If achlorine-containing solvent such as bromochloromethane is used, themixture of the catalyst and the anionic styrenic polymer solution shouldbe formed just before feeding into the reactor to avoid any catalystdegradation which tends to occur over time.

In the case of feeding as in 4) above, the combination of brominatingagent, especially bromine, and anionic styrenic polymer solution shouldnot be preformed and stored for any substantial period of time as thebrominating agent such as bromine will tend to brominate the polymerchain during storage. Thus, as a general rule, if feeding as in 4) is tobe used it is desirable to form the mixture of brominating agent andpolymer solution and feed the resultant mixture into the reaction zonewithin a few minutes after formation, with the shorter the period frommixture formation to feeding, the better.

Irrespective of the manner in which (i), (ii), and (iii) are fed inaccordance with the above, the concurrent feeding of (i) a brominatingagent, preferably bromine, (ii) aluminum halide catalyst in which thehalide atoms are bromine or chlorine or both, and (iii) the anionicstyrenic polymer solution in a solvent does not require that the feeds,be initiated at the same moment of time. For example, if, say, acontinuous feed of (iii) is initiated followed 1 minute later byinitiation of a continuous feed of (ii), followed 1 minute later byinitiation of a continuous feed of (i), the bromination time starts withthe initiation of the feed of (i) because in the prior two minutesbromination pursuant to the invention would not occur. Also slightinterruptions of one or more feeds during continuous feeding of (i),(ii), and (iii) that do not disrupt the overall operation of the processor have an adverse effect upon product composition are acceptable.Naturally, such interruptions should be avoided as much as possible,especially once steady state operation has been achieved.

In each of the process embodiments of this invention the concurrentfeeds of (i), (ii), and (iii) whether separate or with (1) a combinationof any two of (i), (ii), and (iii) as one feed and (2) the third as aseparate feed—which may be in combination with one of the two of (i),(ii), and (iii) present in the combination of (1)—there are differentways in which the actual feeds themselves are fed into the reaction zoneto form a reaction mixture. One way is to have each feed in the form ofa continuous feed stream. A second way is to have each feed in the formof a pulsed feed stream in which time intervals between the pulses aresufficiently short to keep the amount of aluminum halide being fed atabout 0.8 mole percent or less in relation to the molar amount ofaromatic monomer units in the anionic styrenic polymer being fed, and tokeep the amounts of brominating agent and anionic styrenic polymer beingfed proportioned to produce a final washed and dried brominated anionicstyrenic polymer product containing in the range of about 60 to about 71weight percent bromine. In this second way of feeding the respectivefeeds, the pulses as between or among the respective feeds themselvescan either be synchronized to be simultaneous concurrent pulses or to bealternating pulses, or the respective pulses can be unsynchronizedrelative to each other, and in each instance the pulses can be regularor irregular, all with the proviso that the amount of aluminum halidebeing fed is kept at about 0.8 mole percent or less in relation to themolar amount of aromatic monomer units in the anionic styrenic polymerbeing fed, and the amounts of brominating agent and anionic styrenicpolymer being fed are kept in proportions to produce a final washed anddried brominated anionic styrenic polymer product containing in therange of about 60 to about 71 weight percent bromine. A third way is tohave at least one of the respective feeds as a continuous feed streamand at least one other of the respective feeds as a regular or irregularpulsed stream with appropriate time intervals between pulses, againsubject to the proviso just given in connection with the second way offeeding the respective feeds.

If necessary, the feed streams to the bromination reaction zone can bedegas sed to remove dissolved atmospheric gases that may be entrainedtherein. In this way, the possibility of exceeding the pressurelimitations of the bromination reaction system being employed isminimized.

In conducting the bromination process, it can be helpful to initiallyprovide in the reaction zone a quantity of solvent such as the solventused in forming the solution with the anionic styrenic polymer. In thisway, a more dilute and thus less viscous reaction mixture can bemaintained in the reaction zone. If desired, a continuous or periodicseparate feed of such additional solvent to the reaction zone can beemployed. Excessive viscosity in the reaction zone is undesirable as ittends to interfere with continuous intimate contact among the reactioncomponents.

Components (i) and (iii) can be proportioned to produce a final washedand dried brominated anionic styrenic polymers of this inventioncontaining in the range of about 60 to about 71 wt % and preferably inthe range of about 67 to about 69 wt % of bromine. The manner ofproportioning the anionic styrenic polymer and the brominating agent toachieve various desired bromine contents are known to those of ordinaryskill in this art and have been described in the commonly-owned patentsreferred to at the outset of this document.

There are various ways in which the processes of this invention can becarried out. One method, which may be termed a batch or a semi-batchmode of operation involves rapidly introducing as described above,components (i), (ii), and (iii) into a reactor such as a stirred potreactor so that the maximum time that any portion of the components areundergoing a bromination reaction does not result in formation ofproduct containing more than about 600 ppm (wt/wt) of bromobenzeneimpurities. To terminate the reaction, the mixture in the stirred potreactor can be rapidly quenched either by introduction of a quenchingcomposition into the reactor or by dumping or feeding the contents ofthe reactor into a quenching vessel containing the quenchingcomposition. In this way, no portion of the reaction mixture undergoesfurther bromination. So that the last portion of components fed to thereactor have sufficient time to undergo suitable bromination, it isdesirable to stop the feeds and to allow a period of at least 1-2minutes before deactivating the catalyst. This at least 1-2 minuteperiod serves as a residual period for the last portion of thecomponents to undergo bromination. This batch or semi-batch mode ofoperation should involve rapid introduction of the components into thereactor and also sufficiently rapid agitation and efficient cooling ofthe reactor contents so that the reaction temperature is maintainedwithin the above-specified temperature ranges and within a suitablebromination reaction time.

Another mode of operation involves use of a continuous process. In onesuch embodiment of this invention, there is provided a process ofpreparing brominated anionic styrenic polymer having a reduced volatilebromobenzene content, which process comprises:

-   A) causing reaction mixture having a liquid phase, which reaction    mixture is continuously formed from concurrent feeds of components    comprised of (i) a brominating agent (preferably bromine), (ii)    aluminum halide catalyst in which the halide atoms are bromine or    chlorine atoms and (iii) anionic styrenic polymer having a GPC M_(n)    in the range of about 2000 to about 30,000 (preferably in the range    of about 2000 to about 10,000, and more preferably in the range of    about 3000 to about 7000) in the form of a solution in a solvent, to    continuously travel through and exit from said reaction zone    maintained at one or more temperatures in the range of about 10° C.    or less, so that bromination of anionic styrenic polymer occurs    during at least a portion of such travel, the components being fed    being proportioned such that the amount of aluminum halide being fed    is at about 0.8 mole percent or less in relation to the molar amount    of aromatic monomer units in the anionic styrenic polymer being fed,    and such that the dried brominated anionic styrenic polymer referred    to in C) hereinafter will have a bromine content in the range of    about 60 to about 71 wt % and preferably in the range of about 67 to    about 69 wt %;-   B) deactivating the catalyst in, and washing away bromide ions and    catalyst residues from reaction mixture that has exited from the    reaction zone (and preferably continuously deactivating catalyst in    the reaction mixture promptly after it exits from the reaction zone    and washing away bromide ions and catalyst residues from reaction    mixture that has exited from the reaction zone);-   C) recovering brominated anionic styrenic polymer product from the    reaction mixture and drying such product whereby the dried    brominated anionic styrenic polymer has a bromine content in the    range of about 60 to about 71 wt % and preferably in the range of    about 67 to about 69 wt % and a volatile bromobenzene content which    is no more than about 600 ppm (wt/wt) and preferably about 300 ppm    (wt/wt) or less.    Preferably the concurrent feeds in such a continuous process are    conducted either by separately and individually feeding each of (i),    (ii), and (iii) concurrently into the reaction mixture, or by    separately feeding (a) a preformed mixture of components (i)    and (ii) and (b) component (iii) concurrently into the reaction    mixture.

Another continuous process embodiment of this invention is a process ofpreparing brominated anionic styrenic polymer having a reduced volatilebromobenzene content, which process comprises:

-   A) causing reaction mixture having a liquid phase, which reaction    mixture is continuously formed from concurrent feeds of components    comprised of (i) a brominating agent (preferably bromine), (ii)    aluminum halide catalyst in which the halide atoms are bromine or    chlorine atoms and (iii) anionic styrenic polymer having a GPC M_(n)    in the range of about 2000 to about 30,000 (preferably in the range    of about 2000 to about 10,000, and more preferably in the range of    about 3000 to about 7000) in the form of a solution or slurry in a    solvent (preferably a solution in a solvent), to continuously travel    through and exit from said reaction zone maintained at one or more    temperatures in the range of about 10° C. or less, so that    bromination of anionic styrenic polymer occurs during at least a    portion of such travel, said feeds of (i), (ii), and (iii) being in    at least two separate feed streams and with (ii) being kept separate    from at least one of (i) and (iii) until the at least two separate    feeds of (i), (ii) and (iii) directly enter the reaction mixture    and/or are unified (e.g. within a feeding device such as a probe,    injector or nozzle which is injecting the unified feeds into the    reaction mixture) no more than 5 seconds and preferably no more than    2 seconds before emerging from the feeding device and entering the    larger body of the reaction mixture in the reactor, the components    being combined are proportioned such that the amount of aluminum    halide being fed is at about 0.8 mole percent or less in relation to    the molar amount of aromatic monomer units in the anionic styrenic    polymer being fed, and such that the dried brominated anionic    styrenic polymer referred to in C) hereinafter will have a bromine    content in the range of about 60 to about 71 wt % and preferably in    the range of about 67 to about 69 wt %;-   B) deactivating the catalyst in, and washing away bromide ions and    catalyst residues from reaction mixture that has exited from the    reaction zone (and preferably continuously deactivating catalyst in    the reaction mixture promptly after it exits from the reaction zone    and washing away bromide ions and catalyst residues from reaction    mixture that has exited from the reaction zone); and-   C) recovering brominated anionic styrenic polymer product from the    reaction mixture and drying such product whereby the dried    brominated anionic styrenic polymer has a bromine content in the    range of about 60 to about 71 wt % (preferably in the range of about    67 to about 69 wt %) and a volatile bromobenzene content which is no    more than about 600 ppm (wt/wt) (preferably about 300 ppm (wt/wt) or    less).

In conducting this continuous process, preferably the reaction mixtureas continuously formed in A) is comprised predominately or entirely of aliquid mixture, preferably the brominating agent is bromine, andpreferably the bromine is continuously fed within the confines of theliquid reaction mixture being continuously formed. The term “confines”means within the body of the liquid reaction mixture as distinguishedfrom feeding onto an exterior portion of the liquid reaction mixture.Feeding into the confines can be accomplished by use of an injector,nozzle or feeding probe which extends into the body of the liquidreaction mixture in the reactor. In a batch/semi-batch operation in astirred pot type of reaction vessel it is desirable to provide that theemerging feed from each injector, nozzle, or feeding probe is in closeproximity to the periphery of the stirring blades so that the reactantsare quickly dispersed within the body of the liquid reaction mixturebeing formed in the reaction zone and any temperature gradients areminimized.

In the continuous mode of operation the reaction mixture formed in A)from components (i), (ii), and (iii) can be formed in various ways. Forexample, the bromination reaction mixture can be formed by use of atleast two separate continuous feeds of (i), (ii), and (iii) with no suchfeed being formed from all three of (i), (ii), and (iii), all asdescribed above. Also, there can be plural feed inlets to the reactionzone for one or more of (i), (ii), and (iii). Regardless of how manyfeed inlets are used and how the feeds are carried out, the feeds shouldbe substantially concurrent (except at start up when the feeds can bestarted at different times). Slight feed interruptions which cause nosubstantial imbalance in the operation can be tolerated but if possible,should be avoided or at least minimized so that steady state operationmay be achieved. While it is preferred that all such feeds be continuousfeeds, it is deemed possible to operate with one or more pulsed feedshaving uniformly short time intervals between individual pulses. In eachof the foregoing ways of carrying out the feeds in A), a separateconcurrent continuous or discontinuous feed of solvent can be utilizedas another feed stream in A), if desired. As in the case of thebatch/semi-batch mode of operation, it is desirable to have theindividual bromine feed(s) or the feed mixture(s)/solution(s) containingbromine to be fed directly into the confines of the liquid reactionmixture being formed in the reaction zone so that the bromine is rapidlydispersed within such liquid reaction mixture as it is being formed.Thus the reaction zone may be provided with a turbulent flow zone intowhich the individual bromine feed(s) or the feed mixture(s)/solution(s)containing bromine is/are injected into the body of a turbulent reactionmixture as it is being formed in the reaction zone.

In conducting a continuous process of this invention, it is desirable toprovide, maintain, and/or control the rate at which the reaction mixtureexits from the reaction zone in A) in relation to the rate of thefeeding of components (i), (ii), and (iii) into the reaction zone suchthat the volume of the traveling contents of the reaction zone remainssubstantially constant. Thus, it is usually preferable to havecontinuous feeds to the reaction zone and continuous flows from thereaction zone, as this tends to make it easier to maintain anessentially constant volume in the reaction zone. However, it ispossible to use pulsed feeds to the reaction zone or one or more pulsedstreams exiting from the reaction zone while at the same time keepingthe volume of the reaction mixture in the reaction zone substantiallyconstant.

The processes of this invention can be conducted at any suitablepressure. Preferably the process is conducted at a pressure up to about60 psig and more preferably in a closed bromination reaction systemunder autogenous pressure.

Product Workup and Drying

In the practice of this invention the product workup involvesdeactivating the catalyst and washing away bromide ions and catalystresidues (preferably by quenching the reaction mixture with or in anaqueous quenching medium). If any residual bromine remains in thereaction mixture prior to deactivating the catalyst, the aqueousquenching medium should contain a reducing agent such as sodium sulfiteto convert the bromine into bromide ions which are then washed away inthe aqueous phase resulting from the quenching operation, recovering thebrominated anionic styrenic polymer product, and drying the washedbrominated anionic styrenic polymer product. Product recovery andwashing can be carried out as a single unitary operation.

Deactivation of the catalyst in B) of a batch operation is typicallycarried out by quenching the entire reaction mixture with a quenchingcomposition. Deactivation of the catalyst in B) of a continuous processis typically carried out by quenching reaction mixture that exits fromthe reaction zone with a quenching composition as or after such reactionmixture exits from the reaction zone. In either case, the quenchingcomposition typically comprises water in the liquid state. In acontinuous operation the quenching step can be carried out eitherdiscontinuously or continuously. Discontinuous quenching involvescollecting during a short period of time reaction mixture as it exitsfrom the reaction zone and then promptly quenching that quantity in orwith the quenching composition. Continuous quenching involves causingthe reaction mixture as it continuously exits from the reaction zone tobe quenched in or with the quenching composition.

The makeup of the aqueous quenching composition can vary considerably.Typically however, the quenching composition will comprise at leastwater in the liquid state. An aqueous solution of one or more suitablesalts can also be used as a quenching composition. Non-limiting examplesof salts which may be used in forming quenching compositions includesodium sulfite, sodium bisulfite, and sodium borohydride. Temperaturesfor the quenching composition can also vary, but typically will be inthe range of 0 to 30° C. The concentration of the quenching compositioncomprised of one or more suitable salts in water is also susceptible tovariation. In actual practice, in situations where some residual bromineexists in the reaction mixture after removal from the brominationreaction zone, use of 1% to 10% solutions of sodium sulfite in waterhave been found convenient for use as quenching compositions to reducethe bromine to bromide ions which are then carried away in the aqueousphase. However, other concentrations can be used. Preferably, thequenching liquid is composed solely of water.

Product recovery and workup after quenching can be conducted by lettingthe quenched reaction mass settle to obtain a two-phase reaction masscontaining an organic phase, which contains, as a solute, the brominatedanionic styrenic polymer product and an aqueous phase. The aqueous phaseis decanted and the remaining organic phase is stripped of its solventcomponent. It is most convenient to accomplish this strip by pumping theorganic phase into boiling water. As the solvent is flashed off, thebrominated anionic styrenic polymer product forms a precipitate. Theprecipitate can be recovered by any liquid-solid separation technique,e.g., filtration, centrifugation, etc. The recovered precipitated washedproduct is then dried, typically at a temperature in the range of about110° C. to about 150° C.

If desired, the aqueous phase from the quenching operation containingHBr can be treated with a metallic base such as sodium hydroxide,potassium hydroxide, magnesium hydroxide, or calcium hydroxide toproduce the corresponding metallic bromide salt. Preferably, the aqueousphase from the quenching operation can be steamed stripped in either acontinuous or batch operation to remove traces of solvent and therebyprovide an aqueous hydrobromic acid solution suitable for use or sale.

When properly conducted in the manner described above, the brominatedanionic styrenic polymer produced by the process of this invention, willcontain no more than about 600 ppm (wt/wt) and preferably about 300 ppm(wt/wt) or less of bromobenzene impurities.

Components Used as Feeds to the Reaction Zone

In both the batch/semi-batch mode of operation and the continuous modeof operation, various materials can be used as components (i), (ii), and(iii). For example, in all such modes of operation it is preferred touse elemental bromine as the brominating agent. The bromine should be ofhigh purity. Methods for purifying bromine when and if necessary ordesirable are described in many of the commonly-owned patents referredto at the outset of this document. However, other brominating agents canbe used in the practice of this invention. Among known brominatingagents that may be used are bromine chloride, N-bromosuccinimde,1,3-dibromohydantoin, and pyridinium tribromide.

Anionic styrenic polymers which are brominated to form the brominatedanionic styrenic polymers of this invention are homopolymers of styreneor copolymers of styrene with other vinyl aromatic monomers. Amongsuitable vinyl aromatic monomers from which the anionic styrenicpolymers can be formed are those having the formula:

H₂C═CR—Ar

wherein R is a hydrogen atom or an alkyl group having from 1 to 4 carbonatoms and Ar is an aromatic group (including alkyl-ring substitutedaromatic groups) of from 6 to 10 carbon atoms. Anionic polystyreneitself is a preferred styrenic polymer. Use can be made however of otheranionic styrenic polymers such as those made from at least 50 weightpercent, and more desirably at least 80 weight percent of styrene and/oralpha-methylstyrene with the balance being derived from ring substitutedstyrenic monomers. Thus, the “anionic styrenic polymers” used in thepractice of this invention are formed by anionic initiatedpolymerization of one or more styrenic monomers in which at least 50%,preferably at least 80%, and more preferably essentially 100% of thearomatic groups in the polymer have a hydrogen atom on at least oneortho position, and when the ring system of such aromatic groups iscomposed of a combination of phenyl groups and alkyl-substituted phenylgroups, at least 50%, preferably at least 80%, and more preferablyessentially 100% of all such phenyl groups have a hydrogen atom on eachortho position. Non-limiting examples of suitable monomers that may beused for producing styrenic polymers of this invention are styrene,alpha-methylstyrene, ortho-methylstyrene, meta-methylstyrene,para-methylstyrene, para-ethylstyrene, isopropenyltoluene,vinylnaphthalene, isopropenylnaphthalene, vinylbiphenyl,vinylanthracene, the dimethylstyrenes, and tert-butylstyrene. Thosehaving an unfused benzene ring in the molecule (i.e., those that aredevoid of fused ring structures) are preferred.

Thus, the styrenic polymers used in this invention are typicallypolymers made by anionic polymerization procedures. An excellent processfor producing anionic polystyrene is described in commonly-owned U.S.Pat. No. 6,657,028.

Blends or mixtures of two or more anionic styrenic polymers can also bebrominated using a bromination process of this invention. Such blends ormixtures can be composed of two or more different anionic styrenicpolymers made by anionically-initiated polymerization. A blend ormixture composed predominately of at least one styrenic polymer made byanionically-initiated polymerization and a small amount of at least onestyrenic polymer made by free radical-initiated polymerization may alsobe used as the polymer substrate to be brominated by a process of thisinvention, but use of such blends or mixtures is not preferred.

Any of a variety of suitable organic solvents can be used as the solventfor the styrenic polymer. Thus use can be made of such substances as,for example, dichloromethane, dibromomethane, bromochloromethane,bromotrichloromethane, chloroform, 1,2-dibromoethane, 1,1-dibromoethane,1-bromo-2-chloroethane, 1,2-dichloroethane, 1,1,2-tribromoethane,1,1,2,2-tetrabromoethane, 1,2-dibromopropane, 1-bromo-3-chloropropane,1-bromobutane, 2-bromobutane, 2-bromo-2-methylpropane, 1-bromopentane,1,5-dibromopentane, 1-bromo-2-methylbutane, 1-bromohexane,1-bromoheptane, bromocyclohexane, and liquid isomers, homologs, oranalogs thereof. Liquid mixtures of two or more such compounds can beused. Preferred solvents are dichloromethane, dibromomethane, and1,2-dichloroethane. Bromochloromethane is a particularly preferredsolvent.

With anionic styrenic polymers having a weight average molecular weightin the range of about 2000 to about 10,000, preferably the anionicstyrenic polymer solution used will contain in the range of 250 to 700grams of the styrenic polymer per kilogram of solvent. With anionicstyrenic polymers of higher molecular weights the solutions should bemore dilute to compensate for the increased viscosity of such polymersolutions.

Anionic styrenic polymer is predissolved in the solvent prior to use informing the reaction mixture. The reaction zone in a batch or semi-batchoperation should contain a suitable quantity of organic solvent prior toinitiation of the feed of the components of the reaction mixture inorder to provide good heat transfer and efficient mixing in the initialstage of the feeds. In a continuous mode of operation, a separate streamof additional solvent can be fed into the reaction zone, if desired.

The catalyst as used in forming the reaction mixture is at least onealuminum halide catalyst in which the halide atoms are bromine orchlorine atoms. One such catalyst which is very useful in forming thereaction mixture is aluminum tribromide because of its good solubilityin bromine and halohydrocarbon solvents, such as dibromomethane andbromochloromethane. Aluminum halides containing both bromine atom(s) andchlorine atom(s) that may be used in forming the reaction mixtureinclude such substances as aluminum bromide dichloride (AlBrCl₂, Reg.No. 60284-44-8), aluminum dibromide chloride (AlBr₂Cl, Reg. No.60284-43-7), aluminum bromide chloride (Al₂Br₅Cl, Reg. No. 380907-74-4),and di-μ-bromotetrachlorodialuminum (Al₂Br₂Cl₄, Reg. No. 162719-12-2).Aluminum trichloride can also be used as the catalyst as fed to thereaction mixture. In all of the embodiments of this invention, apreferred catalyst as fed to the reaction mixture is aluminumtribromide.

A catalyst solution suitable for either batch or continuous brominationcan be easily prepared by combining solid AlCl₃ (a substance which isnot soluble in bromine) and gaseous HBr in warm (40-50° C.) liquidbromine. A rapid halogen exchange produces a soluble bromoaluminumhalide catalyst and HCl. Use of a catalyst of this type (with or withoutthe copresence of HCl) is particularly preferred. An advantage of usinga catalyst of this type is that the active brominating species (believedto be the bromonium ion, Br⁺) is preformed, and thus the bromination ofthe anionic styrenic polymer initiates very rapidly and with highselectivity.

Product Sampling and Analysis Procedure for Bromobenzene

While other procedures may be employed for determining bromobenzenecontent of a brominated anionic styrenic polymer, use of the followingProduct Sampling and Analysis Procedure is a recommended procedure foruse in determining whether a brominated anionic styrenic polymersatisfies the volatile bromobenzene content specifications of thisinvention. It is not a requirement that the Procedure be used forexample on every quantity of product produced. The Procedure is for useonly if and when a need or desire for a bromobenzene determinationarises.

The Product Sampling and Analysis Procedure is as follows:

Although pentabromobenzene and hexabromobenzene can not be measured byproton NMR spectra, fortunately, the more volatile and undesirableodorous dibromo, tribromo, and tetrabromo species can be analyzed by useof this procedure. Proton NMR spectra are acquired using a Bruker DPX400 MHZ instrument for solutions of about 10 wt % brominated anionicstyrenic polymer in carbon disulfide/dichloromethane-d₂ (32 scans and 5sec pulse delay). Trifluoroacetic acid (1 drop) is dissolved in eachsolution in the NMR tube prior to analysis. After setting the CD₂Cl₂peak (triplet) to 5.3 ppm and baseline correcting the spectrum to removecontributions from the aromatic protons of the brominated anionicstyrenic polymer, the following signals are integrated:

Singlet near 8.1 ppm for 1,2,4,5-tetrabromobenzene

Doublet near 7.8 ppm for 1,2,4-tribromobenzene

Singlet near 7.5 ppm for 1,4-dibromobenzene

The integrals of the brominated anionic styrenic polymer aliphaticregion (0.4 to 3.5 ppm) and aromatic region (5.6 to 8.2 ppm) are alsoobtained. Using these integrals and the molecular weights of thecomponents of interest, the amount of each component is calculated.Summation of the amounts of 1,2,4,5-tetrabromobenzene,1,2,4-tribromobenzene, and 1,4-dibromobenzene defines the volatilebromobenzene content of the brominated anionic styrenic polymer as usedin this invention.

Proportioning of Catalyst

To achieve optimum results, the proportions of catalyst(s) of thisinvention in the range of about 0.8 mole percent or less relative to theanionic styrenic polymer used will vary somewhat depending for exampleon the composition of the catalyst, the optimum results to be achieved,and the makeup and monomeric formula weight of the anionic styrenicpolymer being used. Based on results to date, with AlCl₃ added as thecatalyst and anionic polystyrene with a monomeric formula weight of 104daltons, proportions in the range of about 0.6 to about 0.8 mole % ofAlCl₃ based on the anionic polystyrene being brominated are recommended.Note in this connection, the data in the Table A extracted from the morecomplete data in Table 1 hereinafter, which extracted data focus on theeffect of the molar ratio of AlBr₃ to anionic polystyrene (APS).Relatively simple laboratory bromination experiments can be used in anyother situations to optimize results when practicing this invention.

TABLE A Example Ref. A 1 2 3 AlBr₃, mole % based on APS 1.42 0.72 0.470.35 Bromobenzenes formed, ppm (by NMR) 1,4-dibromobenzene 90 4 20 191,2,4-tribromobenzene 320 0 90 0 1,2,4,5-tetrabromobenzene 870 250 120 0

Note especially the large reduction in total dibromo-, tribromo-, andtetrabromo-benzene content (from 1280 ppm to ca. 250 ppm and lower) forthe brominated APS products achieved at the lower catalyst loadingspursuant to this invention as shown in Table A. The work reported inTable 1 hereinafter further show that with the AlBr₃ catalyst level forthe continuous bromination of APS of Example 2 is adequate to achievehigh bromination (ca. 68 wt %) using a CSTR (continuous stirred tankreactor) average residence time of 8 minutes at a temperature of about1° C. Also shown by the more complete data given in Table 1 hereinafteris that when the AlBr₃ level was reduced to the level of Example 3,bromination was limited to ca. 61 wt %, but bromobenzene formation wasnearly eliminated (19 ppm) while product thermal stability remainedhigh. These results thus indicate that a combination of continuousbromination and use of suitable reduced catalyst levels offers anopportunity to both lower costs and improve quality by significantlyreducing bromobenzene impurity formation.

A reduction in bromobenzene formation was also found for batchbromination of APS when the aluminum halide catalyst level was reduced.Example 4 used about half the level of AlCl₃ as Reference Example B, andthe product had about half the amount of bromobenzene impurities (seeTable 2). An even greater reduction in bromobenzenes was observed forthe product of Example 5 where the catalyst (AlBr₃) was fed to thereaction dissolved in the bromine feed stream. This metered introductionof catalyst to the batch reaction results in the same level ofbromobenzene formation as a comparable continuous reaction (Example 1).

Brominated Anionic Styrenic Polymers of the Invention

Novel brominated anionic styrenic polymers can be produced by use of theprocess technology of this invention. In addition to reducedbromobenzene contents (no more than about 600 ppm, and preferably about300 ppm or less), brominated anionic styrenic polymers of this inventionhave other desirable characteristics and properties. For example,besides bromine contents in the range of about 60 to about 71 wt % andlow bromobenzene contents, the new brominated anionic styrenic polymersof this invention have very desirable thermal properties and colorcharacteristics. These polymers can also have high melt flow indices.Preferred new brominated anionic styrenic polymers of this inventionalso have reduced percentages of aromatic rings with ortho-substitutedbromine atoms. More preferred new brominated anionic styrenic polymersof this invention also either have (A) a thermal stability in the 320°C. Thermal Stability Test of 300 ppm or less of HBr (still morepreferably 200 ppm of HBr or less and even more preferably 125 ppm ofHBr or less) or (B) a thermal ΔE color value by the Hunter test of 15 orless (still more preferably 12 or less). Still more preferred newbrominated anionic styrenic polymers of this invention also have both ofthese (A) and (B) properties.

Desirably, the GPC weight average molecular weight of the brominatedanionic styrenic polymers of this invention is in the range of about10,000 to about 30,000, and more preferably in the range of about 10,000to about 20,000.

Particularly preferred brominated anionic styrenic polymers of thisinvention and especially the brominated anionic polystyrenes of thisinvention, have bromine contents in the range of about 60 to about 71 wt%, bromobenzene contents of no more than about 600 ppm, and morepreferably about 300 ppm or less, and additionally at least one of thefollowing properties:

-   1) a thermal ΔE color value of 15 or less;-   2) a thermal stability in the 320° C. Thermal Stability Test of 125    ppm or less of HBr; and optionally, at least one or both of:-   3) a GPC number average molecular weight in the range of about    10,000 to about 15,000 and a polydispersity of about 1.25 or less;-   4) an initial ΔE color value of 5 or less and still more preferably    3 or less.    Brominated anionic styrenic polymers of this invention and    especially the brominated anionic polystyrenes of this invention,    having any three or all four of additional properties of 1), 2), 3),    and 4) are more preferred.

Of all of the brominated anionic styrenic polymers of this invention,the more preferred are brominated anionic polystyrene polymers.

REFERENCE TO THE DRAWINGS

Reference is now made to the Figures of the Drawings which schematicallyillustrate typical preferred systems for practicing the processes ofthis invention. These Figures are not intended to limit this inventionto only the systems depicted.

FIG. 1, which is not to scale, schematically depicts a typical feedingsystem adapted for feeding a mixture of brominating agent and aluminumhalide catalyst as a preformed mixed feed, and a solution of anionicstyrenic polymer in a solvent as the other feed. In the form depicted,feeding system 10 is basically an annular mixing and injection devicemade of fluoropolymer, that is housed inside a glass-lined dip tube 12for support. Dip tube 12 is typically made of exteriorly and interiorlyglass coated carbon steel and is thus suitable for downward immersioninto the bromination reaction mixture formed from the feeds. Conduits 14and 16 are disposed within the interior of, and extend along much of thelength of, dip tube 10. At its lower end portion, conduit 14 isconstricted into a smaller diameter conduit 22. Conduit 16 at its lowerportion 25 is turned inwardly within plug 18 so that the end portion ofconduit 18 opens into mixing chamber 20 into which the flow from conduit22 is directed. Plug 18 is tightly secured within the interior walls ofdip tube 12 either by virtue of the size of its outer diameter vis-a-visthe inner diameter of dip tube 12 or by use of a plurality of annularsealing rings (not shown) disposed around the exterior of plug 18. Ineither case the bromination reaction mixture is thus prevented frompassing upwardly into the interior space 26 of dip tube 12. Mixingchamber 20 is a sealed enclosure except for the entry openings for thefeeds of conduits 22 and 25 and an axially disposed port opening intodischarge conduit 28. Discharge conduit 28 is typically threaded at itsupper exterior so that it is screw fitted into the lowermost portion ofmixing chamber 20.

In operation, the preformed mixture of brominating agent and aluminumhalide catalyst flows through conduits 14 and 22 and the solution ofanionic styrenic polymer flows through conduits 16 and 25. At mixingchamber 20 the brominating agent and catalyst are traveling in adownward axial direction and the anionic styrenic polymer solution istraveling in a radially inward direction. Thus, the feeds intersect andimpinge perpendicularly in mixing chamber 20 and then within 1 second orless, the resultant mixture is forced through discharge conduit 28 andoutlet orifice 30 and into the bromination reaction mixture.

Typically conduits 14 and 16 are made of ¾-inch O.D. fluoropolymertubing such as Teflon® polymer tubing with an I.D. of ⅝-inch. Conduits22 and 25, plug 18 are also typically made of fluoropolymer. Conduit 22typically has an I.D. of 0.466 inch. Conduit 25 typically has an I.D. of0.3125 inch. Typically discharge conduit 28 has an I.D. of 0.375-inch.In the form depicted in FIG. 1, plug 18 and discharge port 28 thereinextend about ¼ inch below the lowermost rim of dip tube 12. Dimensionsof the schematically depicted feeding system of FIG. 1 can varydepending for example on the scale of operation.

In a typical plant scale operation for a 1714 kilogram/hour feed ratefor a 10% solution of anionic polystyrene having a GPC number averagemolecular weight of 3500 and a feed rate of 712 kg/hour of brominecontaining 0.44 wt % of AlBr₃, the residence time of the mixture formingin mixing chamber 20 is about 10⁻⁴ seconds.

The flow diagram of FIG. 2 schematically depicts one type of system thatcan be used for conducting a continuous process pursuant to thisinvention. Basically the system is composed of a loop type reactor 40, apump 42 for circulating the reaction mixture including the HBr coproductthrough reactor 40, a take-off line 44 for receiving from reactor 40 aportion of the circulating reaction mixture and transmitting suchcontents to a quench vessel (not shown), a dual injection systemcomposed of injector 43 and injector 45, an indirect heat exchanger 46,and a static mixer 48. In the form depicted, heat exchanger 46 isdisposed upstream from injectors 43 and 45 and downstream from pump 42so as to remove heat generated by the action of pump 42, as well as heatfrom the exothermic bromination reaction. If desired, heat exchanger 46can be placed at any other suitable place relative to reactor 40. Alsomore than one such heat exchanger can be employed in association withreactor 40 to remove heat at more than one location around the loop.Heat exchanger 46 is provided with a flow of suitable heat absorbingliquid such as cooling water and/or ethylene glycol.

As depicted, injectors 43 and 45 are in axial opposed alignment. Thoughnot shown in the line drawing of FIG. 2, the orifices of injectors 43and 45 are spaced apart from each other so that the contents of theserespective injectors are forced directly toward each other andsubstantially at right angles into the reaction mixture flowing throughreactor 40. Such an arrangement ensures very rapid contacting among theinjected contents from the injectors and the reaction mixture flowingthrough the reactor. This in turn ensures highly rapid initiation of thebromination reaction.

Take-off line 44 as depicted continuously removes from reactor 40 aportion of the circulating reaction mixture. The contents of take-offline 44 are typically transported to and discharged into a vessel (notshown) containing a quenching liquid which promptly deactivates thecatalyst.

Injector 43 receives and discharges a solution of anionic styrenicpolymer in a suitable solvent whereas injector 45 receives anddischarges a mixture of brominating agent such as bromine, and catalystsuch as aluminum tribromide. If desired, three injectors (not shown) canbe disposed around reactor 40, one for injecting solution of anionicstyrenic polymer, another for injecting brominating agent (with orwithout solvent or diluent) and the third for injecting catalyst (withor without solvent or diluent) so that contact among the three injectedstreams occurs rapidly thus resulting in rapid initiation of brominationof styrenic polymer. In such a three-injector system the three injectorscan be in any disposition relative to each other provided the injectedcontents from the injectors come into contact with each other rapidly,preferably within a matter of a few seconds. One such three injectorarrangement involves disposing the injectors around reactor 40 with therespective axes of the three injectors in the same plane and radiallyspaced at about 120° intervals.

The system of FIG. 2 is typically operated at a pressure in the vicinityof 45 psig. A larger diameter tubular pressure relief drum 47 fabricatedfrom fluoropolymer is disposed in an upright position in the loop ofreactor 40, for example downstream from the locus of static mixer 48 andpump 42 (as shown) so that the flow of reaction mixture passes into theupper end and out of the lower end of drum 47. Drum 47 is closed exceptfor entrance and exit ports at its ends (for intake and outflow ofreaction mixture) and a lateral port near its upper end enablinghydrogen bromide gas (HBr) entrained in the reaction mixture thatescapes from the reaction mixture due to the pressure drop within thedrum, to exit through a lateral port into purge line 49 leading to ascrubber (not shown) containing a liquid to absorb the HBr from the gasstream that exits from drum 47 via line 49.

A preferred feature of this invention schematically depicted in FIG. 3is the discovery that, contrary to expectations, it is not necessary topurge HBr from a loop-type reaction system as is illustratedschematically in FIG. 2. The system depicted in FIG. 3 is identical tothe system of FIG. 2 except that drum 47 and purge line 49 are absent.When operating the system of FIG. 3 at elevated pressures in the orderof about 20 to about 60 and preferably at about 45 psig, all of the HBrcoproduct formed can be retained in the liquid reaction mixture. Thishas the advantage not only of eliminating a need for a separate HBrscrubber from the overall system, but in addition all of the brominevalues in the HBr can be recovered from the aqueous quench of thereaction mixture thus simplifying and reducing the cost of the recoveryof such bromine values. Further, the retained HBr has been observed toreduce the viscosity of the reaction mixture. Such reduced viscositywould enable the bromination process to operate with less solvent orenable use of a moderately higher molecular weight anionic styrenicpolymer with the same level of solvent.

Uses of the Brominated Anionic Styrenic Polymers

The brominated anionic styrenic polymers of this invention can be usedas flame retardants for various polymeric materials such asthermoplastic and thermosetting polymeric materials and resins. Theweight average molecular weights of the polymers that can be flameretarded pursuant to this invention can vary widely, from low molecularweight polymers to very high molecular weight polymers. Methods forproducing the various thermoplastic or thermosetting polymers that canbe flame retarded with the brominated anionic styrenic polymers of thisinvention are known to those of ordinary skill in the art. Other personswho may be unfamiliar with such matters, should refer to the extensiveliterature that exists on such subjects.

Preferably the brominated anionic styrenic polymers of this inventionare used as additive flame retardants for various thermoplasticpolymers. Thus among the embodiments of this invention are flameretardant compositions comprising at least one thermoplastic polymer anda flame retardant quantity of at least one brominated anionic styrenicpolymer of this invention.

Particular thermoplastics with which the brominated anionic styrenicpolymers of this invention can be blended pursuant to furtherembodiments of this invention include polyethylene terephthalate,polybutylene terephthalate, polycyclohexylene dimethylene terephthalate,polytrimethylene terephthalate, blends or mixtures of two or more ofthese, and analogous copolymeric thermoplastic polyesters, especiallywhen filled or reinforced with a reinforcing filler such as glass fiber.Preferred thermoplastic polyesters are polyethylene terephthalate andpolybutylene terephthalate. Polyamide thermoplastics, such as polyamide6, polyamide 6,6, polyamide 12, etc., again preferably when glassfilled, can also be effectively flame retarded in like manner. Otherthermoplastic polymers that can be effectively flame retarded byaddition of a brominated anionic styrenic polymer of this inventioninclude but are not limited to styrenic polymers, high impactpolystyrenes, crystal polystyrenes, polyolefins, ABS, MABS, SAN,aromatic polycarbonates, polyphenylene ethers, and polymer blends suchas aromatic polycarbonate-ABS blends, polyphenylene ether-polystyreneblends, and similar substances. One group of thermoplastic polymerswhich can be effectively flame retarded by use of at least onebrominated anionic styrenic polymer of this invention is (1) athermoplastic styrenic polymer, (2) a thermoplasticacrylonitrile-butadiene-styrene polymer, (3) a thermoplastic polyester,or (4) a thermoplastic polyamide. Conventional additives, such as flameretardant synergists, antioxidants, UV stabilizers, pigments, impactmodifiers, fillers, acid scavengers, blowing agents, and the like, canbe included with the formulations as is appropriate. Preferred polymerblends of this invention do contain a flame retardant synergist or glassfiber filler or reinforcement, and most preferably both a synergist, anda reinforcing fiber and/or filler.

The brominated anionic styrenic polymer flame retardants of thisinvention are used in flame retardant amounts, which typically arewithin the range of from about 5 to about 25 wt %, the wt % being basedon the total weight of the thermoplastic polymer formulation or blend.When used, the amount of reinforcing fillers such as glass fiber willtypically be in the range of up to about 50 wt % based on the totalweight of the finished composition. The amount of flame retardantsynergist, when used, such as antimony trioxide, antimony pentoxide,sodium antimonate, potassium antimonate, iron oxide, zinc borate, oranalogous synergist generally will be in the range of up to about 12 wt% based on the total weight of the finished composition. Departures fromthe foregoing ranges of proportions are permissible whenever deemednecessary or desirable under the particular circumstances at hand, andsuch departures are within the scope and contemplation of thisinvention.

Masterbatch compositions wherein the components except for the substratethermoplastic polymer are in suitable relative proportions but areblended in a smaller amount of the substrate polymer, are also withinthe scope of this invention. Thus this invention includes compositionswhich comprise at least one thermoplastic polymer such as a polyalkyleneterephthalate or a nylon polymer or a high impact polystyrene with whichhas been blended a brominated anionic styrenic polymer (preferably abrominated anionic polystyrene) of this invention in a weight ratio(substrate polymer:brominated polystyrene) in the range of, say, 1:99 to70:30. Such masterbatch blends need not, but may also contain filler orreinforcing fiber and/or at least one flame retardant synergist such asiron oxide, zinc borate, or preferably an antimony oxide synergist suchas antimony trioxide, antimony pentoxide, sodium antimonate, orpotassium antimonate. Typical examples of reinforcing agents or fillersthat can be used include low-alkali E-glass, carbon fibers, potassiumtitanate fibers, glass spheres or microballoons, whiskers, talc,wollastonite, kaolin, chalk, calcined kaolin, and similar substances.Sizing agents can be used with such reinforcing agents or fillers, ifdesired. A number of suitable glass-filled polyalkylene terephthalatesor nylon molding compositions are available on the open market, andthese can be used in preparing the compositions of this invention.

Also provided by this invention are additive blends composed of abrominated anionic styrenic polymer of this invention and a synergistsuch as, for example, a blend of 75 parts by weight of a brominatedanionic polystyrene and 25 parts by weight of a synergist such asantimony trioxide, antimony pentoxide, sodium antimonate, potassiumantimonate, iron oxide, zinc borate, or analogous synergist. Typicallysuch blends will contain in the range of about 70 to about 98 parts byweight of the brominated anionic polystyrene and about 30 to about 2parts by weight of the synergist, with the total of the two componentsbeing 100 parts by weight. Suitable amounts of other suitable additivecomponents can also be included in such additive blends.

Various known procedures can be used to prepare the blends orformulations constituting such additional compositions of thisinvention. For example the polyalkylene terephthalate polymer or a nylonpolymer and the brominated anionic styrenic polymer such as brominatedanionic polystyrene and any other components or ingredients to beincorporated into the finished blend can be blended together in powderform and thereafter molded by extrusion, compression, or injectionmolding Likewise the components can be mixed together in a Banburymixer, a Brabender mixer, a roll mill, a kneader, or other similarmixing device, and then formed into the desired form or configurationsuch as by extrusion followed by comminution into granules or pellets,or by other known methods.

Preferred thermoplastic compositions of this invention have thecapability of forming molded specimens of 1.6 and 3.2 millimeterthickness ( 1/16 and ⅛-inch thickness) that pass at least the UL 94 V2test.

Analytical Methods

Known analytical methods can be used or adapted for use in assaying thecharacteristics of the polymers of this invention. However, thefollowing methods should be used for the sake of consistency.

Total Bromine Content. Since brominated anionic styrenic polymers havegood, or at least satisfactory, solubility in solvents such astetrahydrofuran (THF), the determination of the total bromine contentfor the brominated anionic styrenic polymers is easily accomplished byusing conventional X-Ray Fluorescence techniques. The sample analyzed isa dilute sample, say 0.1-0.05 g brominated polystyrene in 60 mL THF. TheXRF spectrometer can be a Phillips PW1480 Spectrometer. A standardizedsolution of bromobenzene in THF is used as the calibration standard. Thetotal bromine values described herein and reported in the Examples areall based on the XRF analytical method.

Hunter Solution Color Value Test. To determine the color attributes ofthe brominated polymers of this invention, use is again made of theability to dissolve brominated anionic styrenic polymers ineasy-to-obtain solvents, such as chlorobenzene. The analytical methodused is quite straight-forward. Weigh 5 g±0.1 g of the brominatedpolystyrene into a 50 mL centrifuge tube. To the tube also add 45 g±0.1g chlorobenzene. Close the tube and shake for 1 hour on a wrist actionshaker. After the 1 hour shaking period, examine the solution forundissolved solids. If a haze is present, centrifuge the solution for 10minutes at 4000 rpm. If the solution is still not clear, centrifuge anadditional 10 minutes. Should the solution remain hazy, then it shouldbe discarded as being incapable of accurate measurement. If, however,and this is the case most of the time, a clear solution is obtained, itis submitted for testing in a HunterLab Color Quest SphereSpectrocolorimeter. A transmission cell having a 20-mm transmissionlength is used. The colorimeter is set to “Delta E-lab” to report coloras ΔE and to give color values for “L”, “a” and “b”. Product color isdetermined as total color difference, ΔE, using Hunter L, a, and bscales for the 10% by weight concentrations of the product inchlorobenzene versus chlorobenzene according to the formula:

ΔE=[(ΔL)²+(Δa)²+(Δb)²]^(1/2)

320° C. Thermal Color Test. To determine thermal color of a sample, the320° C. Thermal Stability Test apparatus is used. A 2.50±0.01 g portionof the sample is placed into each of four new clean 20×150 mm testtubes. With a neoprene stopper and Viton® fluoroelastomer tubing, eachtest tube is connected to a nitrogen purge line with exit gas from thetest tube being vented to an aqueous caustic scrubber. With a constantnitrogen purge at 0.5 SCFH, the test tubes are heated at 320° C. in amolten salt bath (51.3% KNO₃/48.7% NaNO₃) for 15 minutes followed by 5minutes at ambient temperature. The residues from each test tube arethen combined to provide enough sample for a solution color measurement.A 5 g±0.1 g portion of the residue is weighed into a 50 mL centrifugetube along with a 45 g±0.1 g portion of chlorobenzene. Close the tubeand shake for 1 hour on a wrist action shaker. After the 1 hour shakingperiod, examine the solution for undissolved solids. If a haze ispresent, centrifuge the solution for 10 minutes at 4000 rpm. If thesolution is still not clear, centrifuge an additional 10 minutes. Shouldthe solution remain hazy, then it should be discarded as being incapableof accurate measurement. If, however, and this is the case most of thetime, a clear solution is obtained, it is submitted for testing in aHunterLab Color Quest Sphere Spectrocolorimeter. A transmission cellhaving a 20-mm transmission length is used. The colorimeter is set to“Delta E-lab” to report color as ΔE and to give color values for “L”,“a” and “b”. Product color is determined as total color difference, ΔE,using Hunter L, a, and b scales for the 10% by weight concentrations ofthe product in chlorobenzene versus chlorobenzene according to theformula:

ΔE=[(ΔL)²+(Δa)²+(Δb)²]^(1/2)

DSC Values. DSC values are obtained with a TA Instruments DSC Model2920. Samples are heated from 25° C. to 400° C. at 10° C./min undernitrogen.

Thermogravimetric Analysis. Thermogravimetric analysis (TGA) is alsoused to test the thermal behavior of the brominated anionic styrenicpolymers of this invention. The TGA values are obtained by use of a TAInstruments Thermogravimetric Analyzer. Each sample is heated on a Ptpan from 25° C. to about 600° C. at 10° C./min with a nitrogen flow of50-60 mL/min.

320° C. Thermal Stability Test. To determine thermal stability andestimate the corrosive potential of a sample, the 320° C. ThermalStability Test is used. The test procedure is essentially as describedin U.S. Pat. No. 5,637,650 except that the temperature used is 320° C.instead of 300° C. The reason for using a higher temperature is that thepolymers of this invention do not evolve measurable amounts of HBr at300° C. Thus, in conducting this test, each sample is run in duplicate.A 2.00±0.01 g sample is placed into a new clean 20×150 mm test tube.With a neoprene stopper and Viton® fluoroelastomer tubing, the test tubeis connected to a nitrogen purge line with exit gas from the test tubebeing passed successively through subsurface gas dispersion frits inthree 250-mL sidearm filter flasks each containing 200 mL of 0.1 N NaOHand 5 drops of phenolphthalein. With a constant nitrogen purge at 0.5SCFH, the test tube is heated at 320° C. in a molten salt bath (51.3%KNO₃/48.7% NaNO₃) for 15 minutes followed by 5 minutes at ambienttemperature. The test tube containing the sample is then replaced with aclean dry test tube, and the apparatus is purged with nitrogen for anadditional 10 minutes with the empty test tube in the 320° C. salt bath.The test tube, tubing and gas dispersion tubes are all rinsed withdeionized water, and the rinse is combined quantitatively with thesolutions in the three collection flasks. The combined solution isacidified with 1:1 HNO₃ and titrated with 0.01 N AgNO₃ using anautomatic potentiometric titrator (Metrohm 670, 716, 736, orequivalent). Results are calculated as ppm HBr, ppm HCl, and ppm HBrequivalents as follows:

ppm HBr=(EP1)(N)(80912)/(sample wt.)

ppm HCl=(EP2−EP1)(N)(36461)/(sample wt.)

ppm HBr equivalents=(EP2)(N)(80912)/(sample wt.)

where EP(x)=mL of AgNO₃ used to reach end point x; and N=normality ofAgNO₃. The tubing is thoroughly dried with nitrogen before the nextanalysis. Each day before the first sample, three empty clean test tubesare run as blanks to assure there is no residual hydrogen halide in thesystem.

NMR Analyses

To determine the volatile bromobenzene content of the brominated anionicstyrenic polymers, proton NMR spectra are acquired using a Bruker DPX400 MHZ instrument for solutions of about 10 wt % brominated anionicstyrenic polymer in carbon disulfide/dichloromethane-d₂ (32 scans and 5sec pulse delay). Trifluoroacetic acid (1 drop) is dissolved in eachsolution in the NMR tube prior to analysis. After setting the CD₂Cl₂peak (triplet) to 5.3 ppm and baseline correcting the spectrum to removecontributions from the aromatic protons of the brominated anionicstyrenic polymer, the following signals are integrated:

Singlet near 8.1 ppm for 1,2,4,5-tetrabromobenzene

Doublet near 7.8 ppm for 1,2,4-tribromobenzene

Singlet near 7.5 ppm for 1,4-dibromobenzene

The integrals of the brominated anionic styrenic polymer aliphaticregion (0.4 to 3.5 ppm) and aromatic region (5.6 to 8.2 ppm) are alsoobtained. Using these integrals and the molecular weights of thecomponents of interest, the amount of each component is calculated.Summation of the amounts of 1,2,4,5-tetrabromobenzene,1,2,4-tribromobenzene, and 1,4-dibromobenzene defines the volatilebromobenzene content of the brominated anionic styrenic polymer as usedin this invention.

To determine the extent of ortho bromination of aromatic rings on thepolymer, proton NMR spectra are acquired using a Bruker DPX 400 MHZinstrument at a probe temperature of 120° C. for solutions of about 20wt % brominated polystyrene in 1,1,2,2,-tetrachloroethane-d₂. Afternormal processing and base line corrections, the area of the broad peaksare integrated between 3.8 to 2.2 ppm and 2.2 to 0.9 ppm. The sum ofthese two areas, after correction for end groups and residual solvent,represents the three chain protons per polymer repeat unit. The areafrom 3.8 to 2.2 ppm represents the chain methine proton where theassociated aromatic ring has at least one ortho-bromine atom. Thepercentage of polymer units having ortho ring bromination is determinedfrom these integrals.

GPC Weight Average Molecular Weights

The M_(w) values are obtained by GPC using a Waters model 510 HPLC pumpand, as detectors, a Waters Refractive Index Detector, Model 410 and aPrecision Detector Light Scattering Detector, Model PD2000. The columnsare Waters, μStyragel, 500 Å, 10,000 Å and 100,000 Å. The autosampler isa Shimadzu, Model Sil 9A. A polystyrene standard (M_(w)=185,000) isroutinely used to verify the accuracy of the light scattering data. Thesolvent used is tetrahydrofuran, HPLC grade. The test procedure usedentailed dissolving 0.015-0.020 g of sample in 10 mL of THF. An aliquotof this solution is filtered and 50 μL is injected on the columns. Theseparation is analyzed using software provided by Precision Detectorsfor the PD 2000 Light Scattering Detector.

Melt Flow Index Test. To determine the melt flow index of the brominatedanionic styrenic polymers of this invention, the procedure and testequipment of ASTM Test Method D1238-00 are used. The extrusionplastometer is operated at 2.16 kg applied pressure and at a temperatureof 220°. The samples used in the tests are neat unadulterated samples ofthe polymers being tested.

As used herein, “APS” designates anionic polystyrene, and “BrAPS”designates brominated anionic polystyrene. The term “M_(w)” means weightaverage molecular weight and the term “M_(n)” means number averagemolecular weight, both as determined by GPC (light scattering detector)described above. The term “CSTR” means continuous stirred tank reactor.“BCM” stands for bromochloromethane.

The following Examples illustrate the practice of this invention and arenot intended to limit the generic scope of this invention.

Reference Example A

For this continuous bromination, two feed streams were pumped into thebottom of the glass reactor. The bromine stream, containing thedissolved AlBr₃ catalyst, and the APS solution in BCM were metered tothe reactor using two separate pumps An 80-mL capacity glass CSTR wasused for the reaction. The reactor had an outer insulating vacuum jacketand an inner jacket for circulating glycol coolant. The vessel had twoinlet ports on the bottom for delivery of reagent solutions directlyunder the bottom turbine blade of the dual Teflon turbine agitator(operated at 400 rpm). An overflow port located just above the topturbine blade allowed the reaction mixture to flow by gravity to asplitter that could direct the flow to the main product quench pot (5-Lfully jacketed round bottom flask with paddle stirrer) or a secondarywaste quench pot (2-L Erlenmeyer with magnetic stirrer). Exit gases fromthe CSTR passed overhead through a Friedrich's condenser and into anaqueous caustic scrubber with assistance from a constant nitrogen purgeat the top of the condenser. During the bromination, room and hoodlights were turned off and the reactor was wrapped with aluminum foil tominimize photobromination.

Two identical pumps (Ismatec peristaltic pump, Cole-Parmer SY-78017-00)were used to deliver the bromine/AlBr₃ and APS/BCM solutions to the CSTRusing feed lines of Teflon polymer (⅛″) and Viton polymer (0.10″,Cole-Parmer, SY-07605-46). The operation was started by charging theCSTR with dry BCM (173.7 g) and cooling the contents of the reactor to−6° C. The bromine solution (5.44 g AlBr₃ in 618.2 g Br₂) and APSsolution (150.0 g APS in 1350.0 g BCM, 10.0 wt % APS) feeds to thereactor were started at the same time and both were held constant forthe entire operation. The average bromine feed rate was 1.90 ml/min andthe average APS feed rate was 7.60 ml/min. For the first 30 min ofoperation, the overflow stream from the CSTR was directed to the wastequench pot (containing 530 g of 5 wt % aqueous Na₂SO₃). After thispoint, the overflow stream was diverted to the main quench pot(containing 865 g of 4 wt % aqueous Na₂SO₃) to collect the steady stateproduct until the feed solutions were depleted (77 min). The CSTRtemperature was +2° C. during the steady state operation. The averageresidence time for the reaction mass in the CSTR was 8 min. The organicphase in the main quench pot was transferred to a 2-L separatory funnel.Three aqueous washes (800 g each) were used to remove residual acid andsalts.

The neutralized organic phase was pumped into 4-L of vigorously stirredhot (98° C.) water to obtain a slurry of white finely divided solid inwater. The slurry was suction filtered, and the solid was rinsed on thefilter with water (3×2 L). The wet cake was dried in a nitrogen purgedoven at 130° C. to a constant weight of 317.5 g. Analytical results aresummarized in Table 1.

Example 1

This example of the present invention was carried out as described inReference Example A, except the amount of AlBr₃ catalyst was reducedfrom 5.44 g (1.42 mole % based on APS) to 2.76 g (0.72 mole %). Analysesfor the steady state product are summarized in Table 1.

Example 2

This example of the present invention was also carried out as describedin Reference Example A, except the amount of AlBr₃ catalyst was reducedfrom 5.44 g (1.42 mole % based on APS) to 1.80 g (0.47 mole %). Analysesfor the steady state product are summarized in Table 1.

Example 3

This example of the present invention was carried out as described inReference Example A, except the amount of AlBr₃ catalyst was reducedfrom 5.44 g (1.42 mole % based on APS) to 1.36 g (0.35 mole %). Theincomplete reaction of bromine in the CSTR required the use of moresodium sulfite solution in the main quench vessel (1300 g of 8.0 wt %)to neutralize the excess Br₂, but the rest of the product isolationprocedure was unchanged. Analyses for the steady state product aresummarized in Table 1.

TABLE 1 CONTINUOUS BROMINATION OF APS USING AlBr₃ CATALYST Example Ref.A 1 2 3 APS GPC Analyses M_(n) 3400 3400 3400 3400 M_(w) 3800 3800 38003800 AlBr_(3,), mole % based on APS 1.42 0.72 0.47 0.35 (% of standardcatalyst amount) (001) (05) (33) (52) CSTR reaction temp. (° C.) 2 3 1 1APS Feed Concentration (wt %) 10.0 10.0 10.0 10.0 CSTR ave. residencetime (min) 8 8 8 8 HP-3010 Product Analyses Wt % Br (XRF) 68.5 68.7 67.861.5 MFI (g/10 min, 220° C./2.16 kg) 3.1 2.1 5.7 112 Thermal HBr (320°C./15 min) 147 <50 93 66 Thermal Color (320° C./15 min) L 96.14 97.2995.98 92.21 a −2.83 −1.86 −1.44 −0.61 b 14.30 10.26 10.41 11.50 ΔE 15.0910.81 11.36 14.17 Initial Color, 10 wt % in chlorobenzene L 99.75 100.0099.36 99.75 a 0.02 −0.11 0.02 −0.37 b 0.91 0.97 1.46 1.89 ΔE 1.11 1.011.75 2.02 DSC, T_(g) (° C.) 162.7 166.9 164.8 143.5 TGA 1% wt losstemp., N₂ (° C.) 354.6 358.2 366.1 366.4 BrAPS GPC M_(n) 13,300 13,30013,050 10,450 M_(w) 13,400 13,500 13,200 11,500 % rings with ortho-Br77.7 77.4 71.3 35.2 NMR (ppm) 1,4-Dibromobenzene 90 4 20 191,2,4-Tribromobenzene 320 0 90 0 1,2,4,5-Tetrabromobenzene 870 250 120 0

Example A illustrates advantages of a process in which a short reactiontime and low reaction temperature are used. Examples 1, 2, and 3illustrate the further advantage, pursuant to this invention, of usingin a continuous process a reduced aluminum halide catalyst level alongwith a short reaction time and low reaction temperature. In particular,as seen from Table 1, the combination of these features substantiallyreduced bromobenzene content of the brominated anionic styrenic polymerproduct as produced. Also, thermal properties such as thermal HBr andthermal color were further improved.

Reference Example B

In this batch bromination, a 2.33 g (17.5 mmol, 1.43 mol %) portion ofaluminum chloride (Aldrich) was suspended in 500.2 g of dry (<15 ppmwater) BCM in a 1-L, 5-necked, jacketed, glass reaction flask cooled to−6° C. by a circulating glycol bath. The reaction flask having aflush-mount Teflon bottom valve was equipped with an overhead airstirrer and Teflon banana-blade paddle, Friedrich's condenser (glycolcooled), and thermowell. A constant flow of dry nitrogen was maintainedon the vent line from the condenser to assist in moving exit gases fromthe flask to a caustic scrubber. A 315.0 g (127.6 g APS, 1.225/n mol)portion of the 40.5 wt % solution of anionic polystyrene in dry BCM wascharged to a 500-mL graduated cylinder in a dry box. The graduatedcylinder was then set up to pump the APS solution from the cylinder to ajacketed, glycol-cooled glass mixing tee mounted on the reaction flask.Bromine (529.0 g, 3.310 moles, 2.70 equivalents) was charged to a 250-mLgraduated cylinder and set up to pump the bromine to the same mixing teeas the APS solution. Both streams were cooled separately by the mixerbefore combining at the bottom of the apparatus and dropping into thebromination flask. The reaction mixture was protected fromphoto-initiated aliphatic bromination by turning off hood lights andwrapping the flask and mixing tee with Al foil. Both feeds were startedat the same time and were both completed in 61 min. A rinse of 99.1 g ofdry BCM was used for the APS solution feed system to assure completetransfer of the polymer to the reaction flask while nitrogen was flushedthrough the bromine feed system to give quantitative transfer of thebromine. The reaction temperature was maintained at −2° C. to +1° C.throughout the addition and subsequent 15 min cook period (with nitrogenpurge of the reactor overhead). The catalyst was deactivated by additionof 40 g of water. A 26.5 g portion of 10 wt % aqueous sodium sulfite wasthen added to assure the removal of any residual bromine. The organicphase was separated, and then washed with 800 mL portions of water,dilute caustic, and water. The product was recovered from the washedorganic phase by addition to vigorously stirred hot (98° C.) water. Thesolvent distilled from the hot water leaving a slurry of the brominatedpolystyrene product in water. After suction filtering, the white solidwas rinsed with water (3×2 L) and dried to a constant weight of 382.5 g(98% yield) in an oven (130° C.) under a constant nitrogen purge.Product analyses appear in Table 2.

Reference Example C

In this batch bromination that was carried out in a similar manner toReference Example B, reaction time was reduced from about 76 minutes to35 minutes, and the catalyst was changed from AlCl₃ to AlBr₃. A 2.53 g(9.49 mmol, 1.41 mol %) portion of aluminum bromide (Alfa Aesar) wassuspended in 772.4 g of dry (<15 ppm water) BCM in a 1-L, 5-necked,jacketed, glass reaction flask cooled to −3° C. by a circulating glycolbath. The reaction flask having a flush-mount Teflon bottom valve wasequipped with an overhead air stirrer and Teflon banana-blade paddle,Friedrich's condenser (glycol cooled), and thermowell. A constant flowof dry nitrogen was maintained on the vent line from the condenser toassist in moving exit gases from the flask to a caustic scrubber. A174.3 g (70.6 g APS, 0.678/n mol) portion of the 40.5 wt % solution ofanionic polystyrene in dry BCM was charged to a 250-mL graduatedcylinder in a dry box. The graduated cylinder was then set up to pumpthe APS solution from the cylinder to a jacketed, glycol-cooled glassmixing tee mounted on the reaction flask. Bromine (289.9 g, 1.814 mol,2.68 equivalents) was charged to a 250-mL graduated cylinder and set upto pump the bromine to the same mixing tee as the APS solution. Bothstreams were cooled separately by the mixer before combining at thebottom of the apparatus and dropping into the bromination flask. Thereaction mixture was protected from photo-initiated aliphaticbromination by turning off hood lights and wrapping the flask and mixingtee with Al foil. Both feeds were started at the same time and were bothcompleted in 30 min. A rinse of 100.2 g of dry BCM was used for the APSsolution feed system to assure complete transfer of the polymer to thereaction flask while nitrogen was flushed through the bromine feedsystem to give quantitative transfer of the bromine. The reactiontemperature was maintained at −1° C. to +3° C. throughout the additionand subsequent 5 min cook period (with nitrogen purge of the reactoroverhead). The catalyst was deactivated by addition of 40 g of water. A12.8 g portion of 10 wt % aqueous sodium sulfite was then added toassure the removal of any residual bromine. The organic phase wasseparated, and then washed with 1100 mL portions of water, dilutecaustic, and water. The product was recovered from the washed organicphase by addition to vigorously stirred hot (98° C.) water. The solventdistilled from the hot water leaving a slurry of the brominatedpolystyrene product in water. After suction filtering, the white solidwas rinsed with water (3×2 L) and dried to a constant weight of 205.4 g(95% yield) in an oven (130° C.) under a constant nitrogen purge.Product analyses appear in Tables 2.

Example 4

This batch bromination was carried out as described for ReferenceExample B using the same anionic polystyrene, but with a lower AlCl₃level (1.22 g, 9.15 mmol, 0.75 mol %). Both the bromine and APS feedswere started at the same time and were both completed in 60 min. Thereaction temperature was maintained at −2° C. to 0° C. throughout theaddition and subsequent 15 min cook period (with nitrogen purge of thereactor overhead). The catalyst was deactivated by addition of 40 g ofwater. A 19.2 g portion of 10 wt % aqueous sodium sulfite was then addedto assure the removal of any residual bromine. The organic phase wasseparated, and then washed with water, dilute sodium hydroxide, andfinally water to neutralize acid and remove NaBr. The product wasrecovered from the organic phase by addition to vigorously stirred hot(98° C.) water. The solvent distilled from the hot water leaving aslurry of the brominated polystyrene product in water. After suctionfiltering, the white solid was rinsed with water (3×2 L) and dried to aconstant weight of 378.9 g (97% yield) in an oven (130° C.) under aconstant nitrogen purge. Product analyses are given in Table 2.

Example 5

In this example, the batch bromination described in Reference Example Bwas modified by removing the glass mixing tee and securing the two feedlines together to form a dipleg that delivered the two reagent streamsunder the surface of the solvent in the reaction flask. In addition,AlBr₃ catalyst was used in place of AlCl₃ and it was dissolved in thebromine feed stream instead of being charged to the reaction flask withthe initial solvent charge. The 1-L five-necked fully jacketed reactionflask was charged with 499.9 g dry BCM and cooled to −5° C. The reactantsolutions were then pumped into the cold solvent using an average rateof 2.69 mL/min for the bromine/AlBr₃ solution (526.6 g Br₂ and 2.33 gAlBr₃) and 3.81 mL/min for the APS/BCM solution (315.2 g of 40.5 wt %solution). Both streams were started at the same time. The bromine feedfinished in 64 min and the APS feed ended in 57 min. The reactiontemperature was maintained at −3° C. to +1° C. throughout the additionand subsequent 15 min cook period (with nitrogen purge of the reactoroverhead). The catalyst was deactivated by addition of 40 g of water. A20.8 g portion of 10 wt % aqueous sodium sulfite was then added toassure the removal of any residual bromine. The organic phase wasseparated, and then washed with water, dilute sodium hydroxide, andfinally water to neutralize acid and remove NaBr. The product wasrecovered from the organic phase by addition to vigorously stirred hot(98° C.) water. The solvent distilled from the hot water leaving aslurry of the brominated polystyrene product in water. After suctionfiltering, the white solid was rinsed with water (3×2 L) and dried to aconstant weight of 381.4 g (98% yield) in an oven (110° C.) under aconstant nitrogen purge. Product analyses are given in Table 2.

Example 6

This continuous bromination was carried out similar to Example 1, butusing the same concentrated APS feed solution used for the batchreaction (Reference Examples B and C and Examples 4 and 5). Theoperation was started by charging the 80-mL glass CSTR with dry BCM(163.0 g) and cooling the contents of the reactor to −7° C. The brominesolution (2.29 g AlBr₃ in 525.0 g Br₂) and APS solution (127.5 g APS in187.3 g BCM, 40.5 wt % APS) feeds to the reactor were started at thesame time and both were held constant for the entire operation. Thebromine feed rate was 2.87 ml/min and the APS feed rate was 3.62 ml/min.The CSTR temperature varied from 0° C. to +10° C. during the operation.For the first 25 min, the overflow stream from the CSTR was directed tothe waste quench pot (containing 635 g of 4 wt % aqueous Na₂SO₃). Afterthis point, the very viscous overflow stream was diverted to the mainquench pot (containing 520 g of 4 wt % aqueous Na₂SO₃) to collect thesteady state product. The average residence time for the reaction massin the CSTR was 13 min. The viscous organic phase in the main quench potwas diluted with BCM (288 g), and the lower organic phase was thentransferred to a 2-L separatory funnel. Two aqueous washes (900 g each)were used to remove residual acid and salts. The neutralized organicphase was pumped into 4-L of vigorously stirred hot (98° C.) water toobtain a slurry of white finely divided solid in water. The slurry wassuction filtered, and the solid was rinsed on the filter with water (3×2L). The wet cake (89 g) was dried in a nitrogen purged oven at 130° C.to a constant weight of 45.7 g. Analytical results are summarized inTable 2.

TABLE 2 APS BROMINATION RESULTS Example Ref B Ref C 4 5 6 BrominationProcess Batch Batch Batch Batch Continuous Catalyst AlCl₃ AlBr₃ AlCl₃AlBr₃ in Br₂ AlBr₃ in Br₂ AlX₃, mole % 1.43 1.41 0.75 0.72 0.70 Maximumreaction Temp (° C.) +1 +3 0 0 +10 Total reaction time or 76 35 75 79 13ave. residence time (min) APS feed concentration (wt %) 40.5 40.5 40.540.5 40.5 APS M_(n) 3400 3400 3400 3400 3400 APS M_(w) 3800 3800 38003800 3800 Wt % Br (XRF) 67.3 67.9 68.1 67.6 67.0 Thermal HBr, 320° C./15min/N₂ (ppm) 90 180 119 76 104 Thermal color, (320° C./15 min/N₂), 10 wt% in chlorobenzene L 93.69 89.83 95.45 95.67 88.30 a −3.32 −3.32 −2.31−1.91 −2.62 b 21.86 30.74 14.80 13.70 31.67 ΔE 22.99 32.58 15.70 14.5633.88 Initial Color, 10 wt % in chlorobenzene L 99.63 99.50 99.66 99.2499.22 a −0.71 −0.45 −0.61 −0.55 −0.64 b 2.75 2.64 2.47 2.92 3.61 ΔE 2.922.81 2.63 3.16 3.82 DSC, T_(g) (° C.) 167.4 168.6 166.0 159.9 162.6 TGA1% wt loss temp, N₂ (° C.) 355.4 354.1 352.8 362.3 349.2 BrAPS GPC M_(n)13,000 12,800 13,000 13,200 12,100 M_(w) 13,200 13,200 13,500 13,40012,400 % Aromatic rings with ortho-Br (NMR) 77.0 76.1 72.9 69.7 66.8 MFI(g/10 min, 220° C./2.16 kg) 5.3 5.2 5.7 7.5 12.1 NMR (ppm)1,4-dibromobenzene 270 640 60 40 126 1,2,4-tribromobenzene 450 1040 240130 370 1,2,4,5-tetrabromobenzene 380 280 220 70 1100

The high bromobenzene contents in the product of Example 6 areattributed to the fact that in the continuous mode of operation, thefeed stream of the APS in the organic solvent was too concentrated andthus resulted in a overly viscous reaction mixture. This mixture proveddifficult to handle during workup. Thus, when conducting a continuousoperation, the concentration of the APS in the solution being fed to thereaction zone should be kept more dilute. See in this connection theresults achieved in Examples 1-3 of Table 1.

Other embodiments pursuant to the invention are as follows:

A). A process of preparing brominated anionic styrenic polymer having areduced volatile bromobenzene content, which process comprises:

-   -   A) concurrently feeding into a reaction zone components        comprised of (i) a brominating agent, (ii) aluminum halide        catalyst in which the halide atoms are bromine or chlorine or        both, and (iii) anionic styrenic polymer having a GPC number        average molecular weight in the range of about 2000 to about        30,000 in the form of a solution or slurry in a solvent to form        a reaction mixture, wherein said components are fed (1)        individually as at least three separate feeds or (2) as at least        two separate feeds, one feed of which contains no more than two        of (i), (ii), and (iii), and another feed of which contains the        third of (i), (ii), (iii) either individually or in combination        with no more than one other of (i), (ii), and (iii), to thereby        form a reaction mixture containing a liquid phase, and        maintaining said reaction mixture at about 10° C. or less        whereby bromination of anionic styrenic polymer occurs, the        components being proportioned such that the amount of aluminum        halide being fed is at about 0.8 mole percent or less in        relation to the molar amount of aromatic monomer units in the        anionic styrenic polymer being fed, and such that the dried        brominated anionic styrenic polymer referred to in C)        hereinafter will have a bromine content in the range of about 60        to about 71 wt %;    -   B) deactivating the catalyst in, and washing away bromide ions        and catalyst residues from        -   1) substantially the entire reaction mixture or        -   2) portions of the reaction mixture that have exited from            the reaction zone; and    -   C) recovering brominated anionic styrenic polymer product from        the reaction mixture and drying such product whereby the dried        brominated anionic styrenic polymer has a bromine content in the        range of about 60 to about 71 wt % and a volatile bromobenzene        content which is no more than about 600 ppm (wt/wt).        B). A process as in A) wherein said concurrent feeds in A) are        continuous feeds.        C). A process as in A) wherein said concurrent feeds in A) are        pulsed feeds.        D). A process as in A) wherein at least one said concurrent feed        in A) is a continuous feed and at least one said concurrent feed        in A) is a pulsed feed.        E). A process as in A) wherein said components (i), (ii),        and (iii) are fed individually as at least three separate feeds.        F). A process as in A) wherein said components (i), (ii),        and (iii) are fed as at least two separate feeds, one feed of        which contains no more of two of (i), (ii), and (iii), and        another feed of which contains the third of (i), (ii), (iii)        either individually or in combination with no more than one        other of (i), (ii), and (iii).        G). A process as in F) wherein each of said at least two        separate feeds enters into the reaction zone proximate to the        other feed stream or streams.        H). A process as in F) wherein each of said at least two        separate feeds enters into the reaction zone in substantial        face-to-face opposed alignment.        I). A process as in B) wherein said components (i), (ii),        and (iii) are fed individually as at least three separate feeds.        J). A process as in B) wherein said components (i), (ii),        and (iii) are fed as at least two separate feeds, one feed of        which contains no more of two of (i), (ii), and (iii), and        another feed of which contains the third of (i), (ii), (iii)        either individually or in combination with no more than one        other of (i), (ii), and (iii).        K). A process as in any of A)-J) wherein said brominating agent        is bromine and wherein said GPC number average molecular weight        is in the range of about 2000 to about 10,000.        L). A process as in K) wherein said GPC number average molecular        weight is in the range of about 3000 to about 7000.        M). A process as in E) wherein each of said at least two        separate feeds enters into the reaction zone proximate to the        other feed stream or streams.        N). A process as in E) wherein each of said at least two        separate feeds enters into the reaction zone in substantial        face-to-face opposed alignment.        O). A process as in A) wherein said components (i), (ii),        and (iii) are fed as at least two separate feeds, a first stream        which is formed from bromine and said catalyst and a second        stream which is anionic styrenic polymer having a GPC number        average molecular weight in the range of about 2000 to about        30,000 in the form of a solution or slurry in a solvent; and        wherein said first and second streams enter into the reaction        zone proximate to each other.        P). A process as in O) wherein said brominating agent is bromine        and wherein said GPC number average molecular weight is in the        range of about 2000 to about 10,000.        Q). A process as in P) wherein said GPC number average molecular        weight is in the range of about 3000 to about 7000.        R). A process as in A) wherein said components (i), (ii),        and (iii) are fed as at least two separate feeds, a first stream        which is formed from bromine and said catalyst and a second        stream which is anionic styrenic polymer having a GPC number        average molecular weight in the range of about 2000 to about        30,000 in the form of a solution or slurry in a solvent; and        wherein said first and second streams enter into the reaction        zone in substantial face-to-face opposed alignment.        S). A process as in R) wherein said brominating agent is bromine        and wherein said GPC number average molecular weight is in the        range of about 2000 to about 10,000.        T). A process as in S) wherein said GPC number average molecular        weight is in the range of about 3000 to about 7000.        U). A process as in any of A)-J) or O)-T) wherein the catalyst        is deactivated by quenching the reaction mixture with and        recovering the HBr coproduct in an aqueous quenching medium.        V). A process as in any of A)-J) or O)-T) wherein A) is        conducted in a closed reaction system under autogenous pressure        so that hydrogen bromide coproduct is kept in said reaction        mixture until the catalyst is deactivated.        W). A process as in any of A)-J) or O)-T) wherein said anionic        styrenic polymer is anionic polystyrene.        X). A process as in any of A)-J) or O)-T) conducted as a        continuous process.        Y). A process as in any of A)-J) or O)-T) conducted as a batch        process.        Z). A process as in any of A)-J) or O)-T) wherein said solvent        comprises (a) at least one liquid saturated aliphatic        chlorohydrocarbon, (b) at least one liquid saturated aliphatic        bromohydrocarbon, or (c) at least one liquid saturated aliphatic        bromochlorohydrocarbon, or a mixture comprised of any two or all        three of (a), (b), and (c).

As used anywhere herein including the claims, the terms “continuous” and“continuously” denote that the operation referred to ordinarily proceedswithout interruption in time provided however that an interruption ispermissible if of a duration that does not disrupt steady-stateconditions of that operation. If the interruption is of a duration thatdisrupts steady-state operation, a steady state condition of operationshould be achieved before resuming collection of the product.

Components referred to by chemical name or formula anywhere in thespecification or claims hereof, whether referred to in the singular orplural, are identified as they exist prior to coming into contact withanother substance referred to by chemical name or chemical type (e.g.,another component, a solvent, or etc.). It matters not what preliminarychemical changes, transformations and/or reactions, if any, take placein the resulting mixture or solution as such changes, transformations,and/or reactions are the natural result of bringing the specifiedcomponents together under the conditions called for pursuant to thisdisclosure. Thus the components are identified as ingredients to bebrought together in connection with performing a desired operation or informing a desired composition. Also, even though the claims hereinaftermay refer to substances, components and/or ingredients in the presenttense (“comprises”, “is”, etc.), the reference is to the substance,component or ingredient as it existed at the time just before it wasfirst contacted, blended or mixed with one or more other substances,components and/or ingredients in accordance with the present disclosure.The fact that a substance, component or ingredient may have lost itsoriginal identity through a chemical reaction or transformation duringthe course of contacting, blending or mixing operations, if conducted inaccordance with this disclosure and with ordinary skill of a chemist, isthus of no practical concern.

Each and every patent or publication referred to in any portion of thisspecification is incorporated in toto into this disclosure by reference,as if fully set forth herein.

This invention is susceptible to considerable variation in its practice.Therefore the foregoing description is not intended to limit, and shouldnot be construed as limiting, the invention to the particularexemplifications presented hereinabove.

1. A brominated anionic styrenic polymer having a bromine content in therange of about 67 to about 69 wt %, a volatile bromobenzene content ofno more than about 600 ppm, and the following properties: 1) a thermalΔE color value of about 15 or less; and 2) a thermal stability in the320° C. Thermal Stability Test of about 125 ppm or less of HBr.
 2. Abrominated anionic styrenic polymer as in claim 1 additionally havingthe following additional properties: 3) a GPC number average molecularweight in the range of about 10,000 to about 15,000 and a polydispersityof about 1.25 or less; and 4) an initial ΔE color value of about 3 orless.
 3. A brominated anionic styrenic polymer as in claim 1 whereinsaid volatile bromobenzene content is about 300 ppm or less.
 4. Abrominated anionic styrenic polymer as in claim 2 wherein said volatilebromobenzene content is about 300 ppm or less.
 5. A brominated anionicstyrenic polymer as in claim 1 wherein said brominated anionic styrenicpolymer is brominated anionic polystyrene.
 6. A brominated anionicstyrenic polymer as in claim 2 wherein said brominated anionic styrenicpolymer is brominated anionic polystyrene.
 7. A brominated anionicstyrenic polymer as in claim 3 wherein said brominated anionic styrenicpolymer is brominated anionic polystyrene.
 8. A brominated anionicstyrenic polymer as in claim 4 wherein said brominated anionic styrenicpolymer is brominated anionic polystyrene.
 9. A brominated anionicstyrenic polymer having a bromine content in the range of about 67 toabout 69 wt %, a volatile bromobenzene content of no more than about 600ppm, and the following properties: 1) a thermal ΔE color value of about15 or less; and 2) a thermal stability in the 320° C. Thermal StabilityTest of about 125 ppm or less of HBr, wherein said brominated anionicstyrenic polymer is prepared by a continuous process, which processcomprises: A) concurrently feeding into a reaction zone componentscomprised of (i) a brominating agent, (ii) aluminum halide catalyst inwhich the halide atoms are bromine or chlorine or both, and (iii)anionic styrenic polymer having a GPC number average molecular weight inthe range of about 2000 to about 30,000 in the form of a flowablesolution in a solvent to form a reaction mixture, wherein saidcomponents are fed (1) individually as at least three separate feeds or(2) as at least two separate feeds, one feed of which contains no morethan two of (i), (ii), and (iii), and another feed of which contains thethird of (i), (ii), (iii) either individually or in combination with nomore than one other of (i), (ii), and (iii), to thereby form a reactionmixture containing a liquid phase, and maintaining said reaction mixtureat about 10° C. or less whereby bromination of anionic styrenic polymeroccurs, said feeds of (1) or (2) hereof being fed as continuous orpulsed feeds and the rate at which the reaction mixture exits from thereaction zone in relation to the rate of the feeding of said feeds of(1) or (2) into the reaction zone being such that the volume of thetraveling contents of the reaction zone remains substantially constant,the components being proportioned such that the amount of aluminumhalide being fed is at about 0.8 mole percent or less in relation to themolar amount of aromatic monomer units in the anionic styrenic polymerbeing fed, and such that the dried brominated anionic styrenic polymerreferred to in C) hereinafter will have a bromine content in the rangeof about 60 to about 71 wt %; B) deactivating the catalyst in, andwashing away bromide ions and catalyst residues from 1) substantiallythe entire reaction mixture or 2) portions of the reaction mixture thathave exited from the reaction zone; and C) recovering brominated anionicstyrenic polymer product from the reaction mixture and drying suchproduct whereby the dried brominated anionic styrenic polymer has abromine content in the range of about 60 to about 71 wt % and a volatilebromobenzene content which is no more than about 600 ppm (wt/wt); theprocess being conducted such that the average residence time in saidreaction zone in A) from initial contact of the reactants and catalystin A) until deactivation of catalyst in B) is about 20 minutes or less.10. A brominated anionic styrenic polymer as in claim 9 additionallyhaving the following additional properties: 3) a GPC number averagemolecular weight in the range of about 10,000 to about 15,000 and apolydispersity of about 1.25 or less; and 4) an initial ΔE color valueof about 3 or less.
 11. A brominated anionic styrenic polymer as inclaim 9 wherein said volatile bromobenzene content is about 300 ppm orless.
 12. A brominated anionic styrenic polymer as in claim 10 whereinsaid volatile bromobenzene content is about 300 ppm or less.
 13. Abrominated anionic styrenic polymer as in claim 9 wherein saidbrominated anionic styrenic polymer is brominated anionic polystyrene.14. A brominated anionic styrenic polymer as in claim 10 wherein saidbrominated anionic styrenic polymer is brominated anionic polystyrene.15. A brominated anionic styrenic polymer as in claim 11 wherein saidbrominated anionic styrenic polymer is brominated anionic polystyrene.16. A brominated anionic styrenic polymer as in claim 12 wherein saidbrominated anionic styrenic polymer is brominated anionic polystyrene.